Because you'll eventually get older and more cynical until you become a cranky old man, and then you'll really have a hard time finding a partner for short term gratification.
LOL Actually, if I were a man, I'd remind you of the number of young honeys on the arms of old coots.
My comment was facetious. I think marriage is wonderful. But unfortunately, our society is tending toward hedonism, and marriage and hedoism don't go together.