Totally. I deal almost exclusively in written media, so I don't have a lot of experience with visual art, but you're right...there's not really an archival place to put it the way that AO3 functions for writers. I mean, a person could put art on AO3, but most people don't, and they still have to find a place to host it in the first place. Otherwise, they're relegated to...instagram? Tumblr? Neither are great options.

Of course, image hosting is expensive, so I'm not entirely surprised. It still sucks, though.