>Other currencies get their value because the governments that provide them make people pay taxes
That's demonstrably false, because countries like Zimbabwe and Venezuela experienced hyperinflation (the complete devaluation of a currency) in spite of the fact that their governments were still forcing people to pay taxes with those currencies. So clearly that alone is not enough to provide intrinsic worth to a currency.
Countries like Zimbabwe and Venezuela printed those currencies in vast quantities to pay bills instead of raising [most of] that money through taxes. Taxes owed in previous quarters were worthless compared with the new trillion dollar notes Zimbabwe's central bank issues to pay government officials, and most private transactions were black market so they weren't seeing them returned in taxes. Zimbabwe and Venezuela are the defining example of how a currency which isn't backed by mountains of debt and taxes is reliant entirely on speculators' confidence...
The reason for that devaluation is that trust was eroded. GP's premise is correct, that fiat has value because of governments, but the reasoning here is not fully correct. The value is in the trust that the government and the institutions will continue to function properly.
That's demonstrably false, because countries like Zimbabwe and Venezuela experienced hyperinflation (the complete devaluation of a currency) in spite of the fact that their governments were still forcing people to pay taxes with those currencies. So clearly that alone is not enough to provide intrinsic worth to a currency.