They're buying it from the AI. They haven't produced anything new.

The big issue here is that through all of human history, effort was a necessary prerequisite to making art. Whether that effort came from mixing paint together before sitting down in front of an easel, hiking through the back country to find the perfect spot for a photograph, or fixing n-gons in Blender all evening. If you created a piece of art, there was a shared understanding amongst other artists that you cared enough to put in the work to make something. For most artists, it's the work/journey/process they cherish, not just the end goal. Putting in the work to make your art is usually the only "gatekeeping" that happens in the art community.

But AI is allowing people to short circuit the path from idea -> creation, which begs the question: is that actually creating? Is prompting for a picture substantially any different than tweaking your search on Google images until you find a photo that resembles what you had in mind? Is creating just having a shiny new picture, or is it the hours/weeks/months of effort, failure, and successes that happened leading up to the picture?

Point is: you can call it "gatekeeping" if you want, but all we're really saying is that creation != ideation.