Word order with "do"

[pablostieber]

Why in English are we able to say "Why don't you listen?" but "Why do not you listen?" is incorrect? (Or at least nonstandard.) What is the rule that governs this? Can someone refer me to an accurate grammar guide to explain? An advanced English learner asked me this today in class, and I was, in the moment, unable to offer an adequate answer. Thanks.

[Alan]

Most contractions can be replaced by their original full forms (they've --> they have, he's --> he is/has, etc.), but negative-interrogative verb phrases such as don't you? (--> *do not you?) and isn't he? (--> *is not he?) are exceptions.

There is no specific syntactic "rule" governing this, simply a generalized convention of usage that disallows such full forms for contemporary usage.