I recently spent a long weekend in Las Vegas. The buffets were outstanding, the weather warm and pleasant, and the hotels stunning. (I hadn't been there in probably 10 years — a lot has changed.) But the main reason Las Vegas was a surprisingly relaxing city to spend time in is because it is a city that's authentically unauthentic.
When you visit New York City, you worry about whether you are being a tourist, about whether you are doing as the locals do. Same with visiting Paris, Rome, London. But in Las Vegas, everybody is a tourist. Anybody who's not a tourist works in the tourism/hospitality industry. There is no real thing. It's fake all the way to the bottom. The very idea of a sprawling, water guzzling city that sits in the middle of barren desert is too absurd to take seriously.
There was no sin for me in Sin City, but I still found it a nice place to spend a few days in the winter to overeat, have my photo taken in front of the Effiel Tower, walk the strip, and lie by the pool.