People get stuck on the idea of FOREVER. You can always get a divorce if you don't want to be with them, but accidentally having a baby is a FOREVER problem. Marriage is the contract that protects them. It's also a solution for a time when having an abortion or using effective birth control wasn't an option.

The other thing is, marriage is a very discrete way to use wealth to be with women who otherwise wouldn't date someone. (And it's culturally accepted worldwide)

When I was younger than like 24, I hadn't realized the above yet, so waiting until marriage seemed insane. I don't view it as a big deal anymore, if that's what someone wants it seems like a respectable way to get what they desire.