Because their content is different enough. Getting back to the art example: everyone’s art is unique BUT you can still find other artists that are similar. Sure there will exist other models who look very nearly the same at first glance, but everybody is, in fact, unique! And even two people with nearly identical physiques may create different material. The differences may be subtle to some but very distinguishable to others.

I might just have an eye for the small differences too. I am friends with several people who take lascivious photos of themselves for fun and/or profit. I get to talk with them about it - context, lighting, angles, etc. I just dang ol’ appreciate the craft! It’s not always an attraction thing or arousal thing: the human form is gorgeous and beautiful and utterly divine and manifests in so many different shapes and sizes! And taking well-crafted photographs of any subject is an art!

And maybe that’s why I gravitate towards it - so much pornography is like junk food, but not all adult content has to be! Some of it is like a well crafted meal, featuring quality ingredients prepared well by a skilled cook :)