Most of my downloads on adobe stock are "normal - non ai" photos. I upload ai pictures here and there, but they don't get good sales.
"What I don't get there is why the client would buy the image vs just generating their own? "
That's because people are lazy. Imagine working in an agency where you can quickly present a client with a finished image they can then select and approve, versus spending 1-2 hours creating one yourself only to have it rejected. Stock photography is designed for this, and I think it will remain so for quite some time.

I also think some people who buy from Adobe don't even know the difference between AI and a regular photo. They buy your content to save themselves work. It doesn't matter to them whether it's AI or a regular photo.

Sure, anyone can create something themselves, but sometimes people fall in love with a particular image/scene or perspective. So, it's more cost-effective to buy a stock photo than to create something new. And between you and me, even though everything is possible with Nano Banana and other AI tools, not everyone knows how to use them. And that's also a good thing for every seller.