Relationships, sexual or otherwise, are not subject to paperwork. The days of relationships, sex, or even reproduction being tied to marriage are long gone.
It’s stupid because the combination of singles mixers, tinder, and community events make it very easy to find a partner (keeping them is another story) but nobody wants to try. I’m of the opinion that porn has sapped their will to find women, even though it’s very possible to have a healthy relationship with porn and men have indeed had healthy relationships with porn throughout recorded history.
Some people have decided that they don't need a relationship to be happy. They've found other ways to cope. For some this may be sour grapes. But that's another coping mechanism in itself!