Many women do more than that when they're alone with themselves. But the contrived rules do not allow them to relax with a partner. It is not without reason they say, that a smart woman has it in her head, a fool has it in her mouth. I even know men who categorically reject such liberties.
It's funny, you walk in the room and there's your sister scratching her bald head. Lucky brother to blow such a sexy sister in all the holes.