I tend to go with what TOG said, but it could also be a fetish.
There was a japanese playboy (extremely rich parents) who a few years ago was found with hundreds of videotapes he made of himself having sex with passed out girls. Turns out, some of them he drugged, but many of them he paid to actually sort of "play dead" because that's what turned him on.
I guess somewhere Tom Smothers is having a laugh.*
*For those who don't know, him and Cosby have had a feud going for over 40 yrs. Smothers called him out for refusing to say on their show, what he said to them in private (in regard to race relations and social issues). After Cosby's appearance on their show and Tommy criticizing him, they were at odds for years. In 1976 they were both at a party at the Playboy Mansion and Cosby apparently snuck up behind him, and using Hugh Hefner as a screen hit Smothers with a sucker punch that briefly knocked him out.