The problem is that shit art is what employs a lot of artists. Like, in a post-scarcity society no one needing to spend any of their limited human lifespan producing corporate art would be awesome, but right now that’s one of the few reliable ways an artist can actually get paid.
I’m most familiar with photography as I know several professional photographers. It’s not like they love shooting weddings and clothing ads, but they do that stuff anyway because the alternative is not using their actual expertise and just being a warm body at a random unrelated job.