Both Warren and Sanders have proposed wealth taxes on very high incomes. The proposals call for a 5 or 6% tax on wealth above a threshold in the millions of dollars. Though sales taxes have nothing to do with wealth taxes, they are nevertheless a tax which most people have an instinctive “feel” for (i.e. they know how much it adds to any purchase). Most of us have experience with them with the high end of the range around 8% (in NY for ex.) And the comparison stokes the thought “I pay that level of tax every day so why cant BILLIONAIRES pay it once a year?”
Yes, I know one is a stock and the other a flow. This is marketing, not economics.