I've had it done to me a few times, mostly when I was taking the class on how to do it when I was in massage school. I do it to myself on my neck and shoulders when I can't get into my chiropractor or massage therapist.
I actually do cupping at work but not with fire cups, I use ones with suction. I use it to loosen up tight muscles. It actually works great if you do it right.
I can see how it might make it "sexier" for some people if fire is used, but to me it just seems like more work to do it using fire so I just stick to my suction cups. Plus I don't find it all that kinky or fun to do since it's part of my job lol