I once heard that Whores and pro porn stars always wear their shoes when filming sex or nudity  in bed or any othert place...So for a long time I have observed this to be true,,most of the girls with shoes on are obvious Pros...and perhaps some of the true amateurs imitate what they see in slick porn sites..not ever knowing the meaning of it or caring..I mean give me a break ...high heels in bed ..who knows the origin of it,,?