Like KROC said, I guess it's one of those things people just want to do to put on their resumé.
A cramped seat in cattle class is in no way conducive to bonin'; and only an acutely sex-starved individual would see any appeal in doing it in the lav. First of all, there's the post-proceedings mess; then, there's the whole question of ambiance. Of course, this argument is countered by the "I hate to see an erection go to waste" school of thought.
Personally, I wouldn't consider joining the club in anything less than a spacious first class seat with some nice bubbly on ice next to me. Like that's ever going to happen
But again, sometimes there's something to be said for seizing the opportunity and going with the moment.