I wouldn't be surprised if it's just a case of human nature and ease of promotion.
Humans just naturally have an easier time engaging with pictures with a small amount of text rather than big blocks of text, and comic authors already have a ton of visuals (or can more easily take time to make one) that are somewhat illustrative of the quality of work. It's way harder (and also bad practice) to judge an author's "base quality" from their first paragraph or even first line. Even tradpub books are advertised with their covers and a quote or a short sentence, not the blurb.
Also it could be that in comics even to make a really bad comic there's still going to be a lot of effort that has to go in there to draw the characters, somewhat of a background, letter the bubbles, whereas you could just write a 2000 word chapter on a whim, not do any editing of rereading and hit publish in an hour or two, so if you get into a long running comic even if it's bad you know there's some tenacity to it.
Plus, comics are faster to read and usually shorter due to how long it takes to make 200 words worth of comic, so comics readers can consume comics quicker than any individual author can make them, usually quicker than 10 or 20 even.
Did not mean for this to get so long but generally:
- tapas is known as a comics platform first
- advertising is cheaper and easier for comics because comic authors can (and will) be exploited to make their own promotional materials for free
- comics has a higher barrier for entry so less competition
- comics are quicker to consume so each reader can consume more and more frequently (so more ads for the company)
- in terms of in the forums, there are more threads about comics because its mostly stuff about writing, drawing, and promotion. Comics do all three while writing does only two, so most craft novel threads (unless they're about like narrator voice or setting descriptions) can include comics whereas most drawing threads are comics specific.
To be clear I'm not saying novels deserve less or should just be ok with having less promotion, it would be cool if tapas put more effort into giving promotional tools to their novelists, they just likely won't because capitalism.