Well, how much VAT do you pay on something you buy? It's impossible for you to figure out without having the complete supply chain and pricing details for an item at every step of production. Even seemingly simple products can have many steps in the supply chain where VAT is added. With sales tax, it's right on the receipt and based on the actual price. If it's too high, you know immediately and can complain.

To me, sales tax is much simpler. I also suspect it's significantly less as a percentage of the final price.