Challenging mainstream societies definition of beauty

How come every time, whether the portrayal is on film or television, a sista with a big booty gotta be a hoe, slut, stripper or prostitute? It's just an automatic or a given this is what she is. Why can't a sista with a big booty be a doctor? a lawyer? a professional woman? Or just an average every day woman in an every day role involving every day situations?