How the body is regulated is far from a coherent form of understanding, but it is clear that we need sleep, nutrients,exercise, cleaning of all major systems and proper levels of resources to maintain the body and mind or and soul.
Without some or all of the above we breakdown through fatigue, we rust and self destruct through diseases.
Sleep restores energy levels, completes repairs and cleans and disposed of garbage in the body.
A healthy functional body does more to optimize and correct mistakes.
To go without regular sleep is a form of great harm.