It's good taste to pound a girl's ass! Each of them knows what her pussy is for, but giving her ass to a prick is no easy matter. But when she gets a taste for it, she'll send her dicks up there herself. I know these anal pranksters, but they don't look like they understand.
A lot of girls wouldn't mind getting that kind of medical care! But they just don't meet these doctors, and they are too embarrassed to ask to have it added to their medical records. Look at the fervor with which she is treated in the 9th minute of the video, I even wished I had gone to medical school myself.
I love the binding. It's a situation where the partner is fully exposed. It's easier for him to move on to frank action.