Sex with Prostitutes.

I feel like I'm being stupid but I want opinions. 
Does anyone know if you need to sleep with the prostitutes on Grand Theft Auto to finish your tasks etc? 
I got my boyfriend a PS4 for Christmas and that new GTA game and whenever I'm in the shower or tidying up there's naked animated girls on the screen and he "having sex" with them or "had sex". Does he do it out of choice or do you have too. 
Weirdly it makes me feel crap about myself.