He mentions that sleep is so crucial that despite how vulnerable it makes organisms to be debilitated 8 or whatever many hours a day, what it provides more than counterbalances that massive evolutionary vulnerability.

But to be honest, without light there isn't much humans can do at night.

The forgotten medieval habit of 'two sleeps'

Animals also burn less calories when asleep, meaning they need less food to survive. Any change to sleep less would need to have major benefits of offset the loss of this benefit, as well as only being possible if the "maintenance" need for sleep were reduced or eliminated.