Brilliant theory gerkin!! I�ve come up with my own but yours beats mine hands down. Some of my theories include:-
1) Old fashioned views on sex from our parents (girls play with dolls, boys play with cars, girls are shown how to cook, boys are shown how to fix things, girls and boys are told that inevitably they must marry the opposite sex even though they are nothing alike!)
2) Love is Blind (people love to let their hearts rule their heads which is always going to lead to disaster)
3) People want an excuse to throw an expensive party and receive lots of gifts.