Used to be we thought it was good for burns. Now we know to run cold water on the burn, or just go stand in a cold shower (for a large one).
Used to be we thought it was good for us to eat, made us strong and healthy. We colored margarine just so it would look more like butter. Now we know it (when taken with lots more of the average U.S. diet, which is killing us all by the way) puts a lot of strain on the heart.
Poor butter! It still tastes good on biscuits.