Birds had too different evolution, they have roughly equal hard skills, which isn't true for humans. For humans sperm and eggs are entertainment and are quite high on Maslow pyramid, but the lower levels are solved only by men, and women have only eggs to offer in exchange (also developed plumage), and that's how they adapted, for them sex isn't entertainment, but survival, i.e. they are evolutionarily programmed for prostitution. And sex workers do enjoy sex, like everyone. You better make attractiveness of sex work your point.