Very rarely, although I feel your pain about hotel hair dryers. I usually despise them, but I despise heavy luggage more. I am, in fact, carrying a hair dryer with me on the trip I’m on right now, though—in one of the locations where I’m staying, I didn’t know whether there would be one or not, and I wanted nice hair for that part of the trip too
That said, this trip didn’t require my camera or anything beyond casual clothes, so I’m able to fit the hair dryer in my rollaboard with no problem.