Why Do We Sleep? – Scientific American Blog Network
— Read on blogs.scientificamerican.com/observations/why-do-we-sleep/

We don’t know yet, isn’t that usually the case?

We sleep in theory because we need to rest or replenish the body.

We may only be able to do certain things in sleep to prepare the body for another days use,

Whatever the reason, a good nights sleep can not be substituted with any form of drug or nutrient or better behaviour.

Sleep looks like it is here to stay, like breathing!