C O G N I T I V E
D I S S O N A N C E
You can't even blame it on autism, because if it was just that they'd have a better grasp on the idea that there are "leagues" and that people tend to date in their own. Even that's sort of an autistic way of looking at it, because people can't usually be boiled down to a simple set of stats. But for the most part no one wants to be with someone who has nothing to offer them, because that's just not fair to have to deal with, so we naturally end up pairing off with someone who fits us and our lifestyle.
Generally being the same level of attractiveness, compatible sense of humor, willing to hold down a job and try to improve their life... if too many of these things are missing from one partner, the relationship is going to naturally be difficult for the other one. And as much as these broke, ugly, dumb, "nice" guys might think they want a beautiful wealthy genius as a girlfriend/wife, they really would still be just as miserable if it happened, if not more so. There would be
constant all consuming jealousy, they would be perpetually afraid that their partner would eventually leave (for good reason), and no matter how oblivious they are there would have to be some tiny niggling little voice in the back of their head telling them that they are a burden, not a boon. They love to wallow in pity about how they deserve better, but if they had better they'd gradually start to hate themselves for being dead weight.
That's not being shallow, that's just being realistic, and it applies to every couple regardless of gender.
I can't even understand why you'd want to be with someone if you have nothing to offer them in life.
The Nice Guy honestly believes he's a nice guy
This. A lot this.
The thing so many "nice guys" don't seem to get is that being genuinely nice is a
HUGE draw for attracting a mate. The key though is the word genuine.
Yeah, there's some credibility to the idea that being a bit cocky/bit of a jerk is an attraction feature (and one thing they always leave off is that it doesn't apply just to guys, bitchy girls get a lot of unwarranted attention too), but that's only because the idea is that they're so successful in other areas that they don't have to be nice to you. It makes you wonder what they have going for them that makes them get away with treating people like that.
But being successful and attractive
and being legitimately nice is still a dozen times more appealing to anyone without mental problems.