Three words: World War II.
Recently I went to an organization store to get some supplies and I noticed when the cashier said the amount that the typical price was a bit higher. This is because the retail tax went up.
Grandma recently gave me a talk about taxes and how they started, as a way to raise money for World War II. The intention was to relieve the tax after the war, but it stuck.
Its always nice to get historical perspective as to how come things are the way there are and what it means today.