This thread makes for very sad reading and I really feel for anyone who doesn't enjoy close friendships. A few things do stand out to me, though;
A lot of you seem to have partners - this suggests that at some point, at least, you have been able to meet new people and have been able to develop and maintain a relationship? You're very lucky to have found someone that you click with romantically - some people never find that, and that's a great cause of sadness for them.
However, since you could argue that developing and maintaining a successful intimate relationship is much more difficult than a friendship, playing devil's advocate, can you honestly say that you've focused as much on friendships as you did on your relationships with your partners?Friendships take work too, and if you're always "too busy with my partner and kids" to invest much in a friendship, then you can hardly expect the benefits on demand when you want them.
I'm very lucky and have encountered many people in my life who've wanted to be my friend, but only one who wanted to be my partner. It's odd that so many of you have found the latter but never the former, iyswim?
Secondly, the bitterness about other people's friendships or Facebook updates, or other mums at the school gates is, whilst understandable to a degree I guess, very unattractive. I can appreciate that it's maybe a defence mechanism for some, but that kind of attitude is not likely to endear you to many people.