God how odd where do you live? Basically everyone I know is happily married.
Same here - the only divorced people I know are my parents 
The majority of my friends, colleagues and family are happily married.
I’ve never understood the notion of there being failed marriages everywhere you look and plenty of happy co-habitating long-term couples in their place.
I know a few people who live with their partners but they are either engaged or both on the same page of marriage being on the cards.
The only woman I know who was ‘happily co-habitating’ ended up practically homeless with two children after her partner of 11 years started an affair and she was left with nothing. She was screwed over financially too.
Every woman in a long-term happy cohabitation situation with children believes “it will never happen to me” when it comes to affairs, splitting up, partners getting nasty etc etc but it’s a naive viewpoint.
There are a lot of shitty men out there who can turn and start treating the women awfully, there be abuse going on, having affairs etc which leads to the relationship breakdown, the difference is that married women and their children are protected if that happens whereas in general, unmarried mothers aren’t.
Getting married is wonderful - I personally would have felt quite hurt if my long-term partner hadn’t been willing to make that commitment to me. I wouldn’t have stayed with him because I would always feel that if he wasn’t prepared to commit to me I would always think I was being kept on hand until someone better come along.
However, if two people are on the same page and neither want marriage then their relationship can still happily flourish.
Different people want different things and whatever choices people make are what is best for them as a couple.
But as has been said, marriage offers a lot of security and protection that cohabitation doesn’t.