As an A2 level learner in a foreign country, we were taught that it is imperative to keep the 'pas' in negations, and it's okay to drop the 'ne' in spoken French. But, I observe that the case is exactly the opposite with the phrase "n'importe quoi". Why is the 'pas' left out there?
While doing my research, I did come across this related question, but all it does is explain that there are certain phrases where the pas is dropped without giving any justification about why it is so or how they came to be.
Please do enlighten me if there's something I'm missing.