It all comes to implementation:
A well made romantic subplot may get me more interested, but a badly made one will make me lose interest.
For me it really depends on the series.
If the overarching plot and its subplots had enough to fill each episode/chapter, then a romantic subplot isn't necessary.
Netflix's Lost in Space for example. It's a sci-fi adventure all about problem-solving and discovery with a large focus on the family dynamic of the Robinsons. Definitely doesn't need a romantic subplot in my eyes. Any romance we do get is some teen crushing without heavy focus as of season 2, which is fine and feels natural, and then a rekindling of bonds between the patriarch and matriarch of the Robinson family, which was really good and I loved.
Then you have something like Sense8. While it's pretty action-packed with an interesting plot already, there is a heavy focus on connecting with other people so romance is a natural course for a main and subplot. There are established couples, new couples, couples that don't get together till the very end. Those along with some lovely friendships and parental relationships strengthen the show's themes. And you know what? It all worked excellently together. I loved each and every one of the main and secondary relationships focused on in the show because they felt natural to the characters and the plot.
I'm actually indifferent; I don't care whether there's romance or not in a story (if all else fails, fanfiction is a thing, after all). Really, the building of any relationship (friendship, rivalry, enmity, etc.) is interesting to me; there's more to social intrigue than just romance.
Side note: I wouldn't recommend trying to inject romance into a story to 'appeal to the masses' if you're not actually comfortable with it (or worse, you don't even like it). I'm pretty sure that's how you end up with romantic subplots that are 'shoehorned' in; that distract from the plot...story elements that you don't know how to work with/aren't invested in often end up that way.
I hate romantic subplots.
Not because there's anything inherently wrong with romance, but mostly because the vast majority of romance does not cater to what I think of as attractive/good relationship, so most of the time it just ruins the rest of the IP for me. Like, your usual love interest in a straight romance is actually kinda gross by my standards so I can never sympathise when the on-screen characters are like OMG HE'S SOOOOO HAWT. Like, I have a hot partner of 11 years. If your love interest is not hotter than the real person who sleeps next to me every night, don't try to sell this stuff to me. I legitimately had to put a highly-recommended book down because in the first 30 pages the female character (who is SUPPOSED to be a distinguished mission commander, but whatever) just keeps gushing about how manly and scraggly this guy is and I just kept retching every time she added another descriptor. Oh he's SO MUCH OLDER AND GROSSER-LOOKING THAN ME, TAKE ME AWAY, DADDY! Eugh. Gay/lesbian romances are a little better sometimes because they usually don't feature the nuclear waste pile that is heteronormative standards, but then that brings me to point two...
....Maybe the love interest could be physically attractive, but the way the two characters handle it is absolutely repulsive. Maybe it's toxic, maybe the characters act like toddlers and not the adults that know how to speak that they're supposed to be, maybe the woman(in a straight relationship) is too passive/submissive. Again, it's just cause for frustration and can ruin the rest of the property for me.
So... In theory I'm all for romantic subplots because I like the idea of attractive people getting it on as much as any normal human being, but in practice most of them tend to be an annoyance because they're just not done well.
In my own writing, I do add them if they're natural, but I think on the whole platonic close friendships can be just as interesting of a narrative device as romantic relationships, so I only go the romance route if it actually makes sense. And I greatly enjoy adding already-established romance, like two people who have been together for a while and work well together.
As someone who ships my own characters, yeah, romance as a subplot is great if done right ^^ Though I personally don't mind at all if there is no romance subplot. I agree sometimes it can feel a little out of place. I say if you're doing romance, do it right at least !
When I was a teenager, I had a crush on my science teacher, who was 60 years old. One of my own characters that I consider to be attractive is a 50-year-old woman. So, no, older people can be very attractive. I just find the usual straight dude romantic interest to be kinda repulsive. Much Manly. Very Shovel Jaw. Wow. No grace, no vulnerability, no honesty.
I don't usually care about a romance subplot in the content I consume, because I'd rather have no romantic subplot where there is chemistry than having a shoehorned in subplot. If there's chemistry between characters I usually end up just looking up shipfanart/fanfiction if it isn't the subplot in the story.
I think it depends. I don't actively go looking for stories with romantic subplots, but when they're there and it's written well, I get pretty invested. Most of what I like about the story will be the other aspects of the plot, though.
If they're not written good, well... shudders as I think about all the stories I've read/watched where the romance was so bad it affected the overall quality of the story
Also I sort of agree with Mallory, lmao. I once dropped a book series (spoiler, it was Throne of Glass) for a variety of reasons, but mostly I was sick to death of the MC having a new LI every three books (Last time I read I think she had about four? Including the one that died), and the fact the NEWEST LI was like a piece of carboard whose entire personality was "omg he hot, hot elf boy dedicated to his strong independent gf. look at him, his abs. he's hot"
God, I fucking hated that character lmao.
I think a romance subplot should always be a vehicle of the story's character development & themes. I usually look at it from the concept of an 'impact character', where this character - in this case the love interest - serves as a pivot point to challenge/help solidify the character's views of themselves and the theme. I'm all for a good romance subplot, and it's mostly only gonna feel shoehorned if it doesn't serve the plot at all, and if it doesn't the rest of your story better be damn good or that romance better be cute, or im out.
I love romances, consummated and unrequited, however, I did read some books on the net that had no romance and were extremely easy to invest into. But I like emotional investment from other characters into the main or vice versa. If it is not romantic love, siblings’ feelings, a fan cheering, parental or filial love... basically, I need love in some form to be there to warm up to characters.
Edit: I also wanted to add that it doesn’t matter to me if the romance is straight or not. I find women romantically as attractive as men, so I don’t have any barriers to cheering for any pairings, except obviously abusive relationships.
I'd say that the worst kind of romantic subplot is one put in for the sake of having a romantic subplot, and written by somebody who really isn't invested in it. Don't put one in just for the sake of it, it always feels really forced.
Sometimes friendships are better as friendships. Sometimes a woman doesn't need to be included just so the male protag can kiss her to stop the execs worrying people will think he's gay because he has intense feelings about his male comrades and the male villain. 
But if the creator is really invested in the characters and they have chemistry, I love a good romance subplot! Two characters together dealing with their problems realise they actually might be perfect for each other? Yeah, gimme that! There are two romance subplots that will come up in Errant. One was planned from the get-go, the other happened while planning; the characters just had flaming chemistry in every scene they were in in the drafts, so it was like "oh no, I ship them..." and I really just wanted to. The romance isn't in there because I think it should be, but because I genuinely think those characters make good pairings and I enjoy writing them falling for each other and dealing with their feelings.
I actually think a romantic subplot if done properly is the single best way to improve every non-romance story, and even some ACTUAL romance stories. It's cheesy, but it's also an effective way to make the characters seem more human and relatable, brings a good amount of juicy tension, and often gives readers and viewers an additional reason to root for the characters instead of gambling solely on the main character being charismatic enough for the audience to root for.
Take a show like House MD. Gregory House is a know it all asshole. He's sporadic and treats people like shit, and while he's a brilliant doctor, that wouldn't have carried the show for long. The romantic subplot between him and Lisa Cuddy added that "will they, won't they" sexual tension that lots of viewers love, humanized House enough for the audience to see he's a lot more emotionally-driven than his demeanor would have you believe, and episodes where their relationship progresses are some of the most popular episodes of the entire series.
Now take another series, a series that's practically nothing like House MD... let's use Adventure Time. It's a wacky kid's cartoon full of random events that often turn nonsensical. Yes, there is a great amount of cleverly written lore in the episodes, but undoubtedly a large, if not the majority, portion of the fanbase watch it for the romantic subplots such as Finn's crush on Princess Bubblegum, Princess Bubblegum and Marceline the Vampire's mysterious lesbian-vibe relationship, Finn's relationship with Flame Princess, etc. for pretty much the same reasons that viewers liked the romantic subplot in House MD.
Not every story needs a Romantic subplot. Some stories do just fine without them. And even if they do have one, the romantic subplot doesn't actually have to resolve itself into a relationship between the characters. But it's a very versatile weapon that can definitely give stories that extra appeal.
I dont really go looking for storys with romance, I care alot more about the story itself, the characters motivation and such, but i dont always mind some romance if it doesnt seem forced, like @darthmongoose said it ->
Sometimes you just gotta let a bromance be a bromance...
I actually like these kind of subplots, there can be something there in the beginning but doesnt have to end up in a romantic relationship, the characters can just discover and learn more about each other and end up with a deeper friendship.
And in my own comic some of my first sketches of it was 2 of the characters having some chemistry and my initial idea of how the comic will end has to do with their relationship but im really really bad at writing romance so when ive been sketching out my story, the romance havent really been there as i might have liked it, we'll see if im even going to try, the characters will have to guide me haha 
I'm pretty indiferent to romantic side-plots most of the time. If it's there, then.. Well, it's there. It's not like I can just ignore it or do anything else about it. If it's done well, that's good, but otherwise.. It's still just there. I don't quite understand why I perticularly feel that way towards it when I could put it into my stories with no issue.
Personally, it feels like I get way more out of shipping characters together than I do with the actual relationships written into stories. That's not even something I make the effort to discuss with anyone else in a fandom, just like "these two would be a nice couple, it just makes sense" and that's it
It used to draw me in when I was younger. Now that I'm older it's not necessary however I added romance into my story because imo it adds an extra kick to the story. Shows sides of my character and how they relate with others.
Personally, I think if it's an after thought it doesn't work. Now, if you have love as a main part of it then it can work well.
In my series I have a few love stories woven within and they deal with real life topics like cheating, sexuality, sexual appearance (cross dressing, drag, non-binary are good examples), number of partners (monogamous, poly, FWB, flings/hookups), and societal/cultural norms/expectations (lifestyle choices, arranged, connivence, etc). These stories and situations would not work well if my comic were more light hearted and these were an afterthought. My comic is serious, so it lends itself better to real and messy love.
Yes, love stories do help achieve a broader market, but if it is disingenuous you will lose the main core of readers. Always write for your fanbase. If it happens to have a few "ship" people that's fine, but if that's only 1% of them are you really going to alienate the 99% for the extra 1% growth potentially losing up to 50% of your readership? There's fan comics for the 1% or write a separate short side story. Don't endanger your story if a love story has no place in the plot.
I don't mind them, I just mind if it feels like they're not well done or if they don't fit--like if they're just in a couple episodes and then forgotten forever, or if they're just there when the writer is bored, I guess. Like the romance has to be part of the story, even if it is a subplot--it needs to be thought out with a beginning middle and end (so many times romances are introduced and then just nigh forgotten)
