Up until I married my baker of a wife, I never purchased unsalted butter. She believes that the butter used in baking should always be unsalted so that the salt amount can be more carefully calculated as it greatly impacts baked goods. Also she is first generation in the US with Polish and Hungarian parents, who never used salted butter, but would salt their foods as needed, so it was not a staple in her home growing up. I have adopted the additional butter (unsalted) but we always have salted in the butter dish for bread. This traces back to my childhood when someone (who?!?) had replaced the butter in the butter dish with unsalted butter (which no one seemed to know where it came from). During dinner that evening my mother had smeared some butter on a piece of bread and taken a bite to discover it was unsalted. Through hilarious rounds of accusation about where the butter came from and who put it there, "who put the butter on the plate?" became a household phrase when you couldn't pinpoint who had been the culprit for various things around the house (peed on the seat, ate the last cookie, used the last of the tp, etc).
