Salt is used to preserve butter and other stuff. Hence salted pork, fish, etc.
Butter isn't used to preserve anything that I know of. The fat in it would go rancid.
Unsalted butter is the butter of choice because it doesn't have as long a shelf life (ie: fresher) because it doesn't contain salt and you can add salt to taste.
A
Of course some people might like the heavy pre-salted taste...
>>>April i disagree with you, well partly at least. Yes butter is used as a preservative but for me it is the only butter for bread. It is the only butter I have ever seen in the better restaurants. >>>