Answer: Cause misunderstandings for people who cares about particular grammar.
Explanation: In this case, it's basically using double negatives in a sentence, so (Don't, and No), Are 2 negatives in a sentence, which can cause the sentence to mean something other than what you're trying to get across. So For example: If you were to say (I <em><u>don't</u></em> have <u><em>no</em></u> clue what time it is) It's basically like saying you do have a clue what time it is, it's 2 negatives in a sentence making it the complete opposite.
