Drag to me, I've only seen it like twice for real.. and that's at a gay club. We don't have gay pride parades and the like here, but to me its just a showy way of showing that you're comfortable enough in your own skin and your own sexuality to push these boundaries. Some drag queens do it just for singing shows, dressing up as say Cher, Liza, Dolly, etc...
So to me it doesn't involve any need/desire/sexuality but more or less an entertainment factor and receiving attention.
Oh and straight men dressing up as women for Halloween parties is like an every year thing here... its hilarious really.