People say, "I'm going to sleep now," as if it were nothing. But it's really a bizarre activity. "For the next several hours, while the sun is gone, I'm going to become unconscious, temporarily losing command over everything I know and understand. When the sun returns, I will resume my life." If you didn't know what sleep was, and you had only seen it in a science fiction movie, you would think it was weird.
Imagine if the human species had to hibernate like some other mammals (hibernation is not really necessary in high temperature areas, but lets just say we evolved to do it in the winter). For part of the year, our entire society would shut down. Governments, schools, while everyone hibernated.