Im going to take a stab at this interesting question...

While i don’t do sissy or slut play, Strapon play is my all time favorite. Its easy and tempting to bend genders in a strapon scene.

But I don’t think you have to do it that way. The way the session works for me is not to switch genders but for me as the powerful man getting pegged by a more powerful dominant woman. In my mind that the natural orders of things. I can still be a man she can still be a woman and she can totally have her way with me as i submit to her. I love the thought of her having more power than me. This setup had les to some intense pegging sessions.

Rather its sissy, slut or strapon play many who are interested are probably interested in exploring gender roles and that probably leads to some of it.