It creates a massive market force to drive down sales taxes. You could imagine that most companies would want to be established with lowest sales tax so as to increase their profit margins or to beat the competitive price of goods and services.

So, now, you have a new problem. Top counties with lowest sales tax in the US will massively attract more businesses forcing the rest of the counties to reduce their sales tax too.

The entire problem boils down to federal vs. local control. US is structured with a balance between local, state and federal powers.