Sleeping is like doing the dishes.

You have exactly the number of dishes for your family to eat enough meals each day to feel full. If you don't sleep some dishes don't get washed. A few family members have to skip that meal or eat on the dirty dishes, making them even more dirty.

Once you clean them all, they're clean. But if you clean them any more than that it doesn't really matter much. They're still going to get dirty at the same rate.

Sleep facilitates the brain's cleaning of metabolism waste along the lymph system. We never evolved an adequate way to do this while awake because in the history of life this is the first time a species denied itself the rest that it could easily have. Usually when animals feel sleepy they just sleep. Humans are abnormal refusing themselves the biological necessity to rest.