Account manager sleeps with client to get contract = not prostitution
B-list celebrity sleeps with director to get big role = not prostitution
Journalist sleeps with general to get classified scoop = not prostitution
Employee sleeps with boss to get coveted promotion = not prostitution
Working class but well-read girl with crooked teeth gets paid to go to restaurants with tycoon, sympathise with his first world problems, and later sleep with him = prostitution
(Last example was my neighbour one place I lived)
That's what I mean by how selective the criminalisation is.