Reasons:
Filter words. The sentence has filter words like "might" that diminsh the impact of the sentence.
it doesn't tell us much about either character nor the situation. Like @NetherSlayer said there are so many other options that tell us so much more about the situation even without saying what it is. Especially in comics where the amount of text is limited, you really need your dialogue to pack a punch of subtext (think "For Sale: baby shoes, never worn.")
it can very easily lead into bad exposition in the same way as phrases like "as you know, Bob" can. "As you know, Bob" leads into information that both characters know, so there is no real in-world reason for one to be explaining this thing to the other. "You might want to look at this" can imply it's something not very important or at least not urgent or not directly related to what the character is doing. It only really works in stuff like police dramas and even then it can be overused and the police is a hierarchy so it's more likely that lower status officers would use "might" to their bosses but not the other way around.
unnecessarily cryptic and vague. People don't really talk like that, it's very obviously used to tease the audience so it'll only feel right in certain contexts and tone of story. The closest I've ever heard irl is "I have something to show you", which isn't really the same undertone, it's explicitly saying "there's a think and you need to see it" rather than "I have a thing and maybe if you want I didn't think to show you but now it could be of interest to you".
I have multiple points in my comic where characters are showing eachother stuff, and it's important stuff. I've never had them say "you might want to look at this" nor even "look at this" or equivalent I believe. Characters have either flat out summaried what they're going to look at:
"C'mon, Finn's getting a visual on Haise"
At this point the audience doesn't know who Haise is, but they know the character speaking has been doing some shady business, so that creates the same amount of intrigue if not more than your phrase.
Or the characters looking have explicitly been aware that the others are hiding something from them and both they and the audience will want to find out what it is:
"I know you’ve got information, you think I don’t see your little whispered meetings from down the hall?"
This gives the character still in the dark more agency and it makes the discovery of the information a confrontation, it strains character relationships and asks whether now they're confronted if they will trust the character.
TL;DR: "you might want to look at this" is a placeholder phrase, it holds up but it's there instead of a more interesting dynamic because it's only doing one thing (teasing the audience) rather than a lot of things (giving the audience a bit of info to tease them, show character dynamics, create conflict, add weight to character arcs, reveal insecurities...)