Well, for urban folks.
It started off with Jewish Americans, looking for something that was open to do on Christmas, which turned out to be Chinese restaurants (we have more of them in the US than we do McDonald's) and going to the movies.
But it's such a good idea once kids aren't little and tearing into presents any more that it's become more and more popular among large portions of the population. I wouldn't say it's the dominant way to celebrate Christmas, but I see a lot of people getting Chinese takeout on Dec. 25, when I'm standing in line for my twice-cooked pork.