As far as I know, "Why doesn't he do that?" is perfectly ok.
"Why does not he do that" sounds so rare.
A more common way to say seems to be "Why does he not do that?"
It's rare to find different positioning in contracted form and full form.
Any authoritative comment about this?
Why doesn't he do that? Why does he not do that?
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The phrase "does not" can be used in a subject question, e.g. "Who does not agree with me?", but I wouldn't characterize it as "rare" in any other question form. I would say that it's incorrect syntax.
We form other questions by moving an auxiliary or a copular verb to the beginning of a sentence. We cannot move adverbs along with these verbs. When we form a contraction with an auxiliary and "not", we are really forming a negative auxiliary verb. These contraction function like single words. Otherwise, verb phrases remain as they are sequenced in declarative statements.
"Won't you reconsider?" / "Isn't it ironic?" / "Can't you see what that woman been doing to me?" / "Wouldn't you rather have a V-8?"
"I would rather not, thank you."
We form other questions by moving an auxiliary or a copular verb to the beginning of a sentence. We cannot move adverbs along with these verbs. When we form a contraction with an auxiliary and "not", we are really forming a negative auxiliary verb. These contraction function like single words. Otherwise, verb phrases remain as they are sequenced in declarative statements.
"Won't you reconsider?" / "Isn't it ironic?" / "Can't you see what that woman been doing to me?" / "Wouldn't you rather have a V-8?"
"I would rather not, thank you."