Equally, I've hooked up with some guys who struggle to get off during sex itself (which may be because the grip one uses while masturbating may be firmer than what one experiences during sex).

Having slept with both women and men, I feel like the pressure to reach orgasm seems like it's bad for everyone. One dude I knew felt super insecure about not getting off, which stemmed from a previous partner taking it personally. It's certainly the case that for some men, it can feel uncomfortable to have sex and not reach orgasm. However, I think that everyone would have a better time if people decoupled satisfaction from orgasm.

If I wanted to be certain that I'd get off, then the use of a vibrator helps a lot. That's not necessarily my goal though; some of the best sex I've ever had didn't result in me reaching orgasm, and I find it frustrating when people don't understand that this is possible (I find this problem more common with men). Of course, that's just personal to me — some people may consider reaching orgasm to be an essential part of "good sex", but that's why good communication is the best skill one can develop for better sex.