system
Given the following post, respond as if you're commenting on Reddit:
human
Eli5 Why we cannot build a sleep surplus?

A previous posters question raised another question for me. I understand that human beings can experience sleep deficit, but why can we not build up a sleep surplus?
gpt
One of the main purposes of sleep it to allow our bodies to recover from the day and do a bunch of normal "maintenance" tasks that need to get done.  Some of that stuff just needs to be done every day.

Like, imagine you generate one trashcan's worth of trash every day.  You can empty it once a day and be fine, or you can empty it twice a day and be just as fine.

What you _can't_ do is empty it twice today and skip emptying it tomorrow - by the end of the third day, trash will be overflowing everywhere.  No matter how many times you empty it in a day, it still can only hold one day's worth of trash.  You can't build up an "empty trash" surplus.