They advertise the hell out of hot tubs down here in Texas. There's a very limited time when the weather is cool enough that a hot tub would be enjoyable. I don't get their popularity. I see them on Craigslist in the free stuff section all the time so maybe I'm right. The idea of a hot tub sounds good but the aren't practical.
I had one in Indiana and we could use it pretty much year round.
I don't like saunas but when I went to a gym that had one, I would use them to get rid of a hangover. I would force myself, no matter how shitty I felt to run really hard on the eliptical for 20 minutes then go right into the sauna. I would sweat gallons for about 10 minutes, then be perfectly fine. No hangover, no headache, no alcohol smell. Drink some water, take a shower and be on my way.