This was news to me, from a Paris-trained chef friend.
Butter will keep for weeks or months without refrigeration, depending on how much oxygen it is exposed to. The purpose of a butter dish (or butter crock, etc) is so you can have soft, usable butter on the counter or table at all times, while protected from ambient air.
In fact, butter will stay better and fresher in a butter dish rather than in the fridge where it is exposed to ambient air. Why do Americans keep butter in the fridge? Who knows. It won't melt under 80 degrees F. Supposedly, the butter crocks that use a water seal will keep butter fresh even longer, many months. Well, butter has been around a lot longer than refrigeration.
My days of tearing bread and toast with hard butter are over, as of now. Yes, I do love butter, and even more now that we know it's healthy.