Because they are very lonely. Most of the time, the old Chinese don't live with their children, and because of the limitation of educational level and social conditions, they usually can't find the right way to kill time. The olds in China like to talk about the ways of keeping heathy, a walk after dinner helps digestion; dancing on the square is very helpful both in killing time, talking with freinds and burning energy. Certainly, it is really noisy when they play the loud music, and very hard to the Chinese children who have to study in the late of night.