Why do we have to sleep several hours (4-8) every day?

It seems like such a waste of time, doesn't it? Don't get me wrong, I like to sleep as much as anyone, it is a kind of rejuvenation. I'm no expert, but I do know if we do not sleep for something like 48 hours(2 days) that will literally kill us, we'll die from not sleeping, so somehow our bodies need it to live. I know I do feel crappy if I don't get a good nights sleep! It just seems that on the evolutionary scale of things that we as a species should have developed out of this necessity, somewhere along the line. Maybe it is sound/good sleepers who live longer? I don't know. Any way just something that crossed my mind and I was wondering about. One of the questions I'll definitely be asking God when I see him. Why did you make me this way? O.K. I'm tired, going to bed. Goodnight.