How does that compare to the market depth of actual currencies or commodities? BTC, being objectively worthless, must be much more sensitive to people wanting to sell I'd expect.
There's also other debt that the US government provides in USD - which provides value as well, in the form of bonds.
BTC has no such driver of wealth. Except perhaps money laundering/transfers without AML provisions.
In my view, money is a technology. People use a technology if they find it to be useful. I know this sounds circular, but bear with me. A "major" currency is designed to be useful as a medium of exchange, temporary store of value, and tool of government economic policy. For it to serve these purposes, a government has to moderate its own behavior to some extent.
Thus my view is that the value of a major currency is based, not on the expectation of paying taxes in the future, but on more general expectations of the future behavior of the government.
With that said, paying taxes is good use for money that's a short term store of value, because you rarely need to hold onto your tax money for more than a year before paying it.