Re Only young, unmarried people hang out in groups. Once couples emerge, the social circle narrows... this is mostly true of Americans, but not of other people I know. Americans sit with their spouses when at dinner parties - everywhere else couples split up (because if you wanted to talk to your spouse you could stay home). Many Americans only go out in couples, everybody else has people that one goes out with and people the other goes out with. I have lived on many continents and find this insistence on couples-are-one-person to be singularly American. And stifling to the meetings of individuals, some of whom are single...
I would love to discover a hidden nugget among my friends... but few of them are single. They are mostly in couples who maintain individuality even after pairing up... and I like living in the States. It's luxurious, otherwise.