In at least some cases, it's because of my own willfulness: for example, as I mentioned in On Having No Class, I can't stand wearing much of anything but jeans and tee shirts. I suppose if I worked at if for long enough, I'd find a way.
But I also seem to hav acquired a pretty good knack over the years for making strangers uncomfortable—even when I'm trying to be friendly. I think one reason is that I communicate my own discomfort in my body language, tone of voice, and so on. Certainly it's true that I am usually uncomfortable meeting new people. But then, so too must a lot of other people be who hide it better or something.
There are tricks one can learn, of course. No doubt I've learned quite a few of them myself... I'm not a complete pariah, after all. But the tricks I've heard about—use the other person's name a lot, touch them, ask a lot of questions—are cheap salesman's gimmicks that annoy the living bejeezus out of me when they're used on me. So I can't use them myself in good faith.
I don't want to have to put on an act. A lot of pretty ordinary social behaviors feel to me when I do them like pretending. I hate that. Obviously, we can't go around acting with perfect sincerity at all times. I guess I've sort of decided to deal with this by adopting a relatively flat affect, and this sometimes puts people off.
A related failing, and one which has given me a lot of trouble, is my tendency to emotional outbursts. I'll go on hiding my feelings for as long as I can stand it, then let go with everything I've got. No middle ground.
More generally, I don't seem to do well at any type of negotiation or confrontation. I'd rather pay full price than haggle; rather endure bad service than ask for better.
I'm running out of space. I'll try to sum up. I've paid a considerable price for my various personality quirks. I'm ridiculously well-educated (PhD, Mathematics, 1992) but can't stand looking for a "real" job and very likely couldn't hold onto one even if I could get it. Hence the three different jobs I mentioned earlier.
It's sort of a contemporary cliche that computer skills are the key to good jobs. Hah! I pick that stuff up really easily. What good does it do me if I can't pass the interview? No, the really important thing is presentation. Sincerity. When you can fake that, you've got it made.
So: there's a lot of room in my personality for improvement. Still, change is difficult at best. Even if it were easy, I'm not sure just what or how much I'd change. Maybe it seems like I've been beating myself up here... but the bottom line is, I'd rather be me than have to be anybody else.