I suspect there's a lot more of us than we realize, it's just that we're well spread out. I have a feeling that ESxx types wouldn't mind spending a lot of time with people who function similarily, whereas if you stuck a bunch of INTx people in the same room we'd get bored of the redundancy. However, I doubt that natural selection is sophisticated enough to spread us out like that, so I'm just going to fall back on the whole 'God hates us' argument and be done with it.
This is a slight derail, but I recently read a Newsweek article about men who regularly sold their semen in the early days of artificial insemination. Some of these guys have dozens of children they don't know and can't find. In terms of evolutionary biology, this is better than winning the lottery... twice. If genetic dissemination were like target shooting, then selling sperm would be akin to using a shotgun.
edit: oh, and I bet these guys were NTs. Just a guess.