I agree @Sunshine231 Some posts smack of The Lady Doth Protest Too Much. The absolutely insistence that they're super happy single (from some posters) is a bit odd IMO. If they are soooo happy, they shouldn't feel the need to go on about it. I have seen numerous threads on here about how certain posters LOVE being single. Some actually even titled 'I LOVE being single!' I'm like 'errrr, OK, good for you hun.'
Imagine if someone started a thread saying 'I am SOOOOO glad I am married. I LOVE having a husband!'
They would be torn to shreds.
I never feel the need to start a thread banging on about how happy I am to have a man to share my life with, and my dreams and adventures, and my laughter and tears, and how super lovely it is to be married, so why go on about how wonderful it is to be single? Bit weird.
And whilst I know some marriages are not great, and the couple are not happy, I think there are as many - if not more - unhappy single people. (Not people who have been married/have children/already done the whole family thing, people who have never been married/in a long term relationship.) Many of them are not as super happy as they make out. Quite a number of them struggle not only with loneliness, and having no-one to depend on, or laugh and cry with, and have fun with, but they struggle financially too.
Being perma-single is NOT the wonderful, fun-filled party some posters make it out to be. You do sometimes even see them say they have had people in relationships say they envy them. The vast majority of these people don't, they really don't... Many will be saying it to make the perma single person feel better, and secretly they would not swap places with them. I mean if they did truly want to be single too, they'd just leave their partner. Not that hard to figure out.. 
Oh and as for tor all the posters saying 'leave him' for almost bloody anything, without even trying to figure things out and work through the issues, I believe many of them are single, and miserable with it, and want everyone else to be the same! I have met people like this in real life.