I still don't understand why you would call Champagne something that does not come from Champagne, can't you just call it New South Wales or Napa Valley or wher

I still don't understand why you would call Champagne something that does not come from Champagne, can't you just call it New South Wales or Napa Valley or wherever you are making it? How is it not misleading to call it by the name of a place that it does not come from?