Real Men Go to Sleep
It was my understanding that while Google has nap rooms in some offices, they are seldom used. The culture is geared around long hours and if you are seen to be napping that is seen as a potential sign of weakness. Of course I could be completely wrong (I'm just pulling this idea out of a vague memory of reading about it here on HN) so I hope a Google employee will correct me. However, it seems reasonable that a company would need to do more than just offer the opportunity to take breaks, work from home and work sensible hours. The culture of seeing hard workers as more valuable must be a difficult one to break.