The reason is that politicians of a certain persuasion don’t want taxes to be “hidden.” They want them to be open and explicit to keep people angry at the government for taking so much of their money.

There is, in truth, also an advantage for retailers. They can advertise one price for the whole country, or a whole state or whatever, and not need to worry about the thousands upon thousands of different tax jurisdictions with not only different rates, but different categories that products and services can fall into.

For the consumer, it all means you have no fucking clue what you’ll actually end up paying.