Sleep is highly valued thing here in China. It seems that most Chinese people always ensure they get enough sleep each night, and make sure they have a nap every afternoon after lunch. Actually I hadn't realized siesta was part of Chinese culture before I came here, and certaintly it doesn't have a universally known term like 'siesta' is to the Spanish. When i first arrived i was always puzzled why all the students and staff in the cafeterias would shovel down their lunch then quickly disappear. Now I know. At the current university i'm based at, they switch all the lights off in the cafeteria after an hour to politely knudge you out of there. That's when the sleeping bag and dunas come out onto the tables and the kitchen staff have their snooze. I'm not sure if all white collar workers take naps in their offices at work, but certainly all the Chinese teachers at university do it. and forget about getting any service from the departments or admin offices between 12-2pm, because nobody will be there.
More than anything else though, I think that just because it's more socially acceptable to look tired in public, people let themselves go. I myself often feel tired throughout the day, so i can see myself going flacid and floppy if I wasn't so stuck in my western ways.
Yep chinese people are not afraid of sleeping anywhere at anytime. A while ago i came accross an album dedicated to asian students sleeping in Universities in the west.
http://asianssleepinginthelibrary.tumblr.com/
Just goes to show that westerners find it peculiar to see such an openness to sleep in public! Living here in China though I can't complain. Since I do look like a local I can do as the romans do and now blissfully sleep anywhere I like without so much as a sideward glance from passersby. after securing my wallet of course! 
