My dad also taught us to drink it black. He told us we might be out on a military patrol or forest fire fighting crew someday “and there won’t be any *** **** cream and sugar! Learn to drink it black!” He had stories of being on patrol in Germany right after the war and boiling water in bucket, dumping in the coffee, then cold water to settle the grounds.
Mine weaned me off milk and sugar for that reason. He did it by slowly limiting the milk and sugar and after a while I actually began to taste the coffee, not the additives.