Is there a clear distinction in English between "why" and "what for" ? In french it's literally the same words ("pourquoi" vs "pour quoi")
My 5yo daughter asked me "why do we exist". I answered the why as in some events that happened that led to our existence, but finding a reason is a bit tougher :)
Not a completely clear one, but "what for" is more precise than "why", which can be asking "for what purpose" or "due to what cause".
"Why are you in my room" is obviously asking the former, "why are the cookies burnt" fairly obviously the latter (unless you really did deliberately burn them to achieve some particular further goal...).
My 5yo daughter asked me "why do we exist". I answered the why as in some events that happened that led to our existence, but finding a reason is a bit tougher :)