Foreign Affairs and International Trade Canada advises that,
Although a passport is not required for entry into Mexico, most airlines departing from Mexico are now refusing boarding to Canadians returning to Canada without a valid passport...
Hang on, hang on: the Canadian government does not require Canadians to have a passport to re-enter Canada (at least when travelling from Mexico), but since some airlines are taking it upon themselves to require such, anyway, the Canadian government is advising their citizens to make sure and get a passport for such travel.
Doesn't that sound a bit like the tail wagging the dog, there? Or do I not undersand?