There are many different answers to this, and most of them are probably true. But what is your own personal opinion of why sleep is needed?
I sleep because it helps me feel better each time that I wake up. There are chances of one developing one sickness or another if they fail to sleep for days. Also, the death rate would worsen as long as more people have the power to skip sleeping. So, for these reasons, I believe sleep is very important for good health.