For simplification. If a pound of coffee is bought at Costco, it's hard to figure out if it is for household consumption or for a business. The business might sell a cup of coffee, or it could be a hotel that gives away free coffee to its guest.

So, at least for sales taxes, it is easier if everyone just pay it and the claim it at the end. It's the same as income taxes, where a set amount is deducted on a pay check and the taxpayer gets a refund at the end of the year.