I mean, society pretty much demands extroversion, which can cause an introvert who doesn't know any better to think they're somehow wrong or broken, but that doesn't mean they are.
Are you sure that's true in that generality? Sure, there's shitty people like that who push folks to do stuff they're not comfortable doing, but I've never heard anyone call a kid with one or two close friends and not much social life beyond that a horrible freak who should be purged from the gene pool or something. Might be skewed perception on your side.
(Or on mine, since I never really had that sort of trouble. But eh, that's a possiblity that's impossible to rule out, I guess.)
More about the amount of forced social interaction in schools and workplaces, and how life is much, much easier for those people who are naturally energized by those environments. I am at a huge disadvantage in an office environment mostly keeping to myself as much as I can get away with and just doing good work vs the social butterfly who is the first to know everything, makes friends with all the right people, and goes home fucking refreshed at the end of the day. Since becoming a manager and increasing the amount and nature of my workplace social interaction, I literally have a social hangover every Saturday, where the weight of it all caves in on me and I feel sick and exhausted and don't feel like doing anything the entire day.
And maybe it's not the best model of social behavior, but being on the less understood side of things, it's wonderful to have that model to help explain and teach people to appreciate my needs vs theirs. When I discovered this concept and started reading up on it, I found countless introverts who grew up actually believing there was something wrong with them or that they really didn't like people, because that's what their social environment raised them to believe about themselves, until this model provided them an alternative.
And it definitely has nothing to do with having any sort of misanthropic nature. There are social groups that actually makes me feel energized when I'm around them, and I truly enjoy the interaction. But afterwards, I crash. Hard. And the extroverts in my life can't relate to why whatever I do next has to in isolation.
I suspect that part of the reason you can't relate to this, Helgo, is because U.S. culture favors extroversion to an extreme. A boisterous nature is heavily idealized here, even if it's mean-spirited, and automatically wins you favor much of the time. It's possible to literally get by better than most in this country by socially muscling your way around with nothing but puff and bluster. Look at Trump.
Edit:
Also, this isn't entirely anecdotal, pseudo-scientific junk. Introverts have generally lower thresholds of stimulation than extroverts. This has been studied and linked to brain chemistry. And it's not about putting people's personalities in strict categories. It's a spectrum that describes tendencies.