Port stars cumming

Is it just me? I've noticed a lot of male porn stars can not cum unless they jerk off for several minutes, I mean really your having sex with another person and there ass-mouth-pussy can not make you cum? And please dont say its for the facial shot, ive been with alot of people you don t
have to jerk off for the facial.
Wich leads to another ? When your doing a facial please stroke slowly, when your going crazy with your hand you can't see anything!
Just my observations!!