I have a friend who is quite happy to bed guys but doesn't wnat to wake up beside them in the morning. She's quite happy with that situation, but I think that our hardwiring doesn't usually allow us to do that. Goes back to basic instinct, I think - men may have the urge to spread their genes as far and wide as possible but women have more limited options for reproduction and have the responsibility for the resultant sprog, so try to 'pin' the man down as a provider - to ensure the survival of their genes! No wonder there's such a gender gap!