when i arrived in shanghai two years ago, one of the first things i noticed was sleeping people everywhere. in shops, on the bus, on the train, along the streets, in offices ... at any time of the day - people were sleeping in any weird position - no matter if they were at work or at home.  i thought, “not too bad”  and stayed.
after some time i understood: they are working 7 days a week, 14 hours a day - a good reason for taking the chance of a nap in any “free” minute.  
then in my first apartment on my first bed, i realized this is bloody hard.  after one week i bought a mattress - “cloudsoft” -  against all protests of my curious neighbor (“toooo soft - too warm - not healthy!!”) the average summer temperature in shanghai is between 30 and 40 degrees c, 70-80% humidity - so many people prefer to sleep on a hard bed with only on a bamboo mat on it. the softer the more hot and sweaty - they prefer cool but hard ...
now - after having spent two years in china and one week in the guest bed of my parents in law i finally found out the truth:
people in china take any opportunity for a nap during daytime because over 2000 years ago some maniac told them a hard bed is healthy!  this is what  makes them suffer  every damned night  - they have no choice - they are just fucking exhausted!