Yeah, not really my thing too. But it was very well explained here - it was the first time that I kind of understood what people might get from it...

I got that from The Original Sinners which is actually written by someone who lives this life style. It was a slow walk into their world. But still mostly I didn't really "get" it on the personal level, what people truly gains from it. With some characters it just "works" but with other not so much. Or maybe it's hard for me to get that they are one thing in "real life" and a different person alone in the bedroom.