It is a well-worn trope, but it's not just within christian colleges. I've seen it at several universities that have nothing to do with religious schools. Even

It is a well-worn trope, but it's not just within christian colleges. I've seen it at several universities that have nothing to do with religious schools. Even then, I think a lot of that is just observational bias from the life situation of people in their early twenties, which is when people often start to settle down. So the most inclined to settle down just happen to be in college.