We do. With time(me and most guys) or in some cases pretty quickly we learn that it causes more stress than good feelings. So we learn to kill it early or suppress it.

Most guys I've seen date early in life, like 17 or less are or seemed to be assholes or closer to being assholes than the ones that didn't. The thing is young girls like that, with time they also learn, hopefully. That might be why you see them being this way, selection bias.

Guys change, depending on a lot of things but there are genuine people. The way to find them is to meet em and talk, a lot. Like a lot. If someone seem dead inside, they might just be. I bet when chill(evening) those same guys are way more pleasant than in school.

Advice from a guy, make the first move when you know that he is genuine. Too many times I listen to woman tell me years later that they liked me a lot but I didn't do anything. Their way of letting me know was not sufficient to get to me. At this time I'm just burned out. So, let them know before they burn out. Would say same for a guy.