Because there is a school of thought out there that claims being on your "best behavior" at first is the best way to go.
Because women like me who are exactly what they say they are and don't believe in wasting time talking about the fucking weather but believe in hitting all the taboo subjects as soon as possible are deemed too intense and not fun and scare men away.
Because there would be no reason for divorce if you didn't get a chance to find out how she changed AFTER you married her.