Hmm... my best guess is that when you're thinking of asking them out, or actually going out with them you think about them in many more ways than just sex, and it's only in the back of your mind. You appreciate them more in otherwords, and are thinking more about advancing the relationship.

After you've broken up, you think... damn.. she was pretty hot......... and you know the rest.

You make a good chopper challenge competitor by the way.