In my experience, even though all men know that all men masturbate, A LOT, we rarely talk about it. Oh, we acknowledge and insinuate. Talk around it. Allude to it. But we seldom face right the hell up to it unless we feel pressed to talk about it clinically. (Doc! Gimme some of them magic blue pills!)
I think that subconsciously, men feel masturbation is a weakness, like an admission that we weren’t virile enough to have sex with a real live partner. Plus, as kids, many of us were shamed. (Get your hand out of your pants, you disgusting child!)
So, it’s just not often a subject for comfortable conversation.