Far from all Incels are antisocial. An incel is just a (typically young and male) nonbreeding human of breeding age. Most species have them. Human societies in the past got around the problem a little by discouraging polygamy and shifting enough risk of death onto men only that men were a minority and likely to breed by default if they made it into adulthood. Modern society doesn't like fifteen year olds dying in farming accidents or warfare, so there are a lot of men involuntarily celibate instead. But that category covers a huge range of situations and behaviors. It's just become associated with the antisocial subset because it's an effective insult - by definition, no one wants to be incel.