There are many theories of why people are willing to hold fiat money without any explicit backing. One theory that I’ve never been very fond of is that the ability to pay taxes with cash is what gives fiat money value. This caught my attention:
DENVER (AP) — A marijuana business in Colorado has filed a lawsuit against the Internal Revenue Service for assessing a penalty for paying taxes in cash.
The IRS charges a 10 percent penalty on cash payments for federal employee withholding taxes. But many marijuana businesses are forced to pay taxes in cash because of difficulty accessing banking services
Thus it seems like taxes are one of the very few things that you cannot pay for in cash, at least not without a sizable penalty.