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.
The master was having fun with two girls at the same time. In addition to making the lesbians do their partner cunny, he also tied them up, spanked them, used toys. And then watched them.