Well, as an artist who has worked on collaborations before I can agree and put some imput into it
Definetly this usually happens when there is nothing to gain for the artist, this usually happens when the story, characters, plot, genre, everything is solely of the Writer and the artist is only a means to an end.
This also happens the other way around if the roles are inverted, the writer is the one making something that is solely from the artist, their idea, their characters, their plot, genre, etc.
Actually, if a writer sees their own ability as easy, then of course is going to undercharge for them, I can easily see both writers and artist charging way lower than the minimum wage. I've also seen several writers who have already built quite a fanbase, an income or simply have writing as a second career or hobby, to pay for artist long term (I've been drawing for a writer for almost 4 years now, shameless promo to Scarlet Society, Yandere City -series TBA- and Love Quotes)
Some collaborations do actually work, the thing is that most of the time since there is not a balance, and one will likely take advantage of the other, or demanding way more than what one is offering, then of course, these are going to likely fail if there isn't clear communication. Most of the time, collaborations that have an idea born within two, have higher chances to grow compared to others where the goals, the structure and more are solely of one person and the other is there being a tool to achieve those things.
I believe this is more of a problem about not knowing how to properly promote yourself, a lot of the time I see writers or comic artists dumping their episodes with very irregular schedules, posting every day or all of a sudden posting every now and then, and while there is no rule about doing things specifically, if you want to have a steady pace, build expectation and interest from a reader, then you'll need to construct a way to leave your readers with wanting to read more, but at the same time giving them the space to breath from your series. I also see a lot of them not understanding or not caring enough to see what kind of formula works better on the platforms that they post.
A lot of people also have the terrible bad habit of being... capricious, that they want their story to be LIKE THIS, I WANT IT TO BE THIS WAY! I DONT' WANT TO SEEK ALTERNATIVES! Like, if you assume writing is easy, a lower skill, then... shouldn't be easy for you to write a novel instead of a comic? But everyone wants everything the easy way, they want fame now, they want followers now, they want their story to be a comic, they want people to have the same level of interest and compromise as if we are them.
Or you can always try to date a writer/artist and try to pay them with food, love, being pampered and watching series together, like @Kuma and I do