Hmm.. I'll throw in my $0.02.
I don't know a lot of people that are on anandtech.. but I know a lot of people who would fit in here just fine. Of these people, I'd say most (practically all) are single. They seem to waffle between "I'm glad I don't have to put up with a girlfriend" or "I don't have time to deal with a girl right now" or "I haven't found someone I'm really interested in," or some even live in an odd delusion that they DO date, when in fact, they do not. (going out with friends, "group dates" where there happen to be girls in attendance, etc)
I think the reality of the situation is, most of them are
1) afraid of rejection
2) socially unskilled
3) not convinced that they could get whatever girl they're after, and thus project an insecure image of themselves
4) in denial that they want to date someone
5) setting their sights so high, they have no chance anyway, which is guaranteed rejection and easier to deal with
6) dealing with baggage from their 1st/2nd relationship gone bad (prob their fault) and instead of dating to get over it, are just moping around the house on friday and sat nights
But, in truth - most of them wouldn't have a hard time landing a girl, if they made some simple changes to themselves, and actually got up the nerve to talk to one. What's ironic is that it really only takes one girl to be interested in you, to make you realize you've got a chance with others, and give you the confidence to go out and date.
Of course, being in a relationship isn't necessarily what everyone is looking for. But I'd have to guess that most of the people who say it isn't, are lying. At the very least, I'm pretty sure most of them wouldn't mind getting a little action. And the truth is, it is NOT that hard, it's not a big deal, and for every 20 girls that say no, one is going to say yes. And for every 10 that say yes, at least a couple of those will turn out to be people you're actually interested in pursuing a 'real' realationship with. If not, hey, you date a while, you both learn something about people, and if you're lucky it won't necessarily end on a bad note.
There are very few "problems" with people that make them "undateable" that can't be solved. Guys, usually it's just a matter of cleaning yourself up (go to the mall, buy some new clothes, get a haircut, stop being a fat slob) and making the slightest effort towards a girl you have a realistic shot at. She'll clean you up the rest of the way, and if it doesn't work out, you're better for the experience. As for being a single girl - there's no excuse - there is absolutely no shortage of guys who will try to sleep with you - and you never know, one of them might work out. Ditto with guys, if you have a good job, drive a nice car, etc, believe me there's a girl out there who would love to help you spend your money. ;-) But in between all this, there's really someone for everyone - but the people who hide under a rock and expect them to show up on their doorstep are only hurting themselves. It's very romantic to say you're waiting until you meet "the one," but the truth is, you'll probably meet her, go out with her a few times, then do something so incredibly stupid that she'll leave you and not look back. Unless you're one of those people who always gets everything right on the first try, there's a lot to be said for a little practice. Social situations are no different than anything else.
Ok, it was $0.04.