Among heterosexuals, I have read that only a tiny minority practice it regularly. Most of us consider it gross for the very rational reason that the male and female genitalia have far more nerve endings which produce far more pleasurable responses than an organ designed merely to expel poop.
For normal people, washing the anal region in the course of personal hygiene produces near zero sexual pleasure.
Washing your heterosexual partner's frontal genitalia, on the other hand, can produce intense sexual pleasure only somewhat short of the pleasure produced by penetrative vaginal intercourse.
Bottom line :
Male homosexuals = Dangerous practices
Female lesbos : Not hurting anyone as long as they are NOT raising boys. Then its child abuse. Otherwise I see the government is studying why they are obese.