Why doesn't he masturbate?

I'm curious as to why a man wouldn't masturbate. My boyfriend doesn't masturbate and can't come when he tries to. But he's always ready to have sex. 
I just curious, does he find masturbation lonesome, athletic, not stimulating, embarrassing? I've heard that this is rare. He definitely has health sex drive but he can't reliever sexual tension himself which is why he doesn't even bother with porn. 
Has anyone had experience with this?