Being a Strictly fan, some dancing certainly looks as though it is a prelude to sex, very romantic too, even though it isn't! Nothing to do with being gay, when you think back to dancers like Ian Waite doing the jive with Darcey. If you haven't seen it it's worth a look, on You Tube. Ian looks as though he has been given his birthday and Christmas presents all at once!
As for the Argentine tango - wow.
Sometimes there is a dance routine with all the men dancing, another with all the women. They generally mix up at the end. Doubt they all go off and have sex afterwards.
I love dancing & watching it, all sorts. Also quite happy to dance alone if I have music on that makes me feel like it. I can be more inventive on my own, not afraid to make an idiot of myself. The curtains can figure too but I've never felt sexy with a drape.