In reply to Bob_the_Builder:
Perhaps the rational is that men's brains and women's brains are different and that women generally have less spatial awareness. That would imply being less good at parking. (Women's brains are meant to be better at other tasks such as communication and language.) I think there is scientific research that supports these claims but I'm no expert.
There must have been a reason for them to go to the trouble of implementing this policy.