It depends on how far you’re willing to go before you accept the reason as true without needing further explanation.
If the answer is ‘because the brain needs sleep’ the next question is ‘why does the brain need sleep?’ and not being satisfied by ‘it just does’, there is a desire for an explanation of what sleep does to the brain. And then you will wonder why these processes can’t happen while being awake? What is it about sleep that allows this ‘recharging’ to happen, and what are we ‘recharging’ anyway? Why can’t ‘toxins’ (what are toxins?) be removed while we’re awake?
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