Lets face it. There are significant assymetries between the genders as far as sex is concerned. Women are a lot more selective than men and find way fewer men sexually desirable than vice versa.
Consequently, a significant portion of the male population struggles to be sexually desirable to women.
The prevalence of monogamy and long term relationships hide this gender assymetry to some extent and this remains the default way for the vast majority of men to have sex.
But in this day and age, when marriage and relationships are becoming increasingly fickle, people are postponing settling down until much later, and women and hot men are freely having casual sex, hook ups, flings as long they dont find their Mr/Ms Right; it would be unfair to tell the majority of men that like good little boys, they should be at their best behavior and wait until a woman finds them acceptable enough as a long term partner. P
Paid sex is inevitable if you want to reduce the sexual asymmetry between women and men.