Some items taxable, some are not. Keep track. Some have different rates depending on who's buying, keep track. Buyers in different locations pay different rates, keep track. The rules change frequently, keep track. Collect money for the govt, keep track. Remit quarterly or face penalty.

There complexity and overhead on sales taxes; more than on an income, retained earnings or wealth taxes.

Also, sales taxes take more percent of wealth away from the lower wealth bracket than from the upper wealth bracket.