The history on this is pretty pathetic. The 96 code changed a long standing rule, until then the frames of dryers could be grounded with the neutral. Why, you may ask ? It was allowed during WW2 to save copper and not many troubles were reported, finally, based on evidence (people literally dying) it was addressed in the 96 code. Unfortunately, there are LOTS of installations that grandfather. There were too many instances of housewives (or children playing) behind the dryer (cleaning,chasing a ball....) touch the frame of the dryer, and lean into a water pipe, now you're carrying the neutral current. Too darned many were seriously shocked and more than one expired.
