It depends on the agency. Most will handle any marketing aspect for you. They'll also handle any ideas for shooting new sets and promotions. They'll either take a commission from 20-30%, or they'll pay you a flat fee and take whatever profits the set makes, and pay you an extra bonus if it goes over a set amount. It's probably not a bad business if you're good at marketing considering how many women are turning to OF, especially social media influencers that already had a large following.
But the appeal I'd assume is not doing any of the leg work to get more outreach so all they have to do is get naked on camera lol