Artists consider skill and human expression to be vital components of the artistic process, while developers consider them inefficiencies to be optimized away in pursuit of a minimally viable product. And the end result tends to be a homogeneous, mediocre pastiche of other better artists' work and/or bizarre AI slop.
Also because corporations are training AI on artists' work without their consent in order to automate them out of the industry.
This has been debated and litigated here ad nauseum so here are some articles: