Why is unsalted butter specified in recipes that also add salt? Why not simply use sa

Why is unsalted butter specified in recipes that also add salt? Why not simply use salted butter?

It may seem confusing to add salt to recipes that also call for unsalted butter, but this way the cook is able to control the amount of salt in the dish. It is much better to add the seasoning with your own hand than to rely on an outside source, since different brands vary in salt content.

Also, butter is regulated and graded by the amount of butterfat it contains. The higher the butterfat, the higher the grade it is awarded. Salted butter is often made from a lower-grade butter. In fact, salt has been used for centuries to conceal flavors. I always use unsalted butter, also known as sweet butter, for all recipes.