While some people are immature when they get married, they will eventually grow up. The problem is, when the other spouse, also immature still, can’t wait a bit. It should take between 12-20 months for the average person to mature.
There are people who will never mature either. They will be 70 year old babies, the older they get the more hopeless the situation becomes. Those are a different story altogether. And they’re definitely not as common and is a whole separate discussion.
And yes, some people are mature enough when they get married but that’s not the discussion here.
I don’t think that we in the CR can do much about it. Bigger and stronger people tried.