So it has ever been. At the same time, girls are thinking 'romance, love and marriage'. In short, boys are feral animals at that age, while girls are idealistic and naive.
I guess its too late to go back to "shotgun weddings", ie. "you break it, you buy it".
Assuming no babies are involved, do these really work out well? I can't imagine a girl wanting to be married to some dirtbag she just met.