The craziest part is that has basically replaced the stock photo and royalty free images market, but that market wasn't really any different than the generated image market. There never was much paid to artists; it's more of a marketing and business development business.

Sure, the most well regarded science fiction and fantasy artists get covers painted just for their books, but otherwise it's usually something off the shelf. I've seen unrelated book covers with the same image.

It's no different outside of publishing, with the same smiling families showing up in advertisements for all sorts of businesses.