"Of course, we could just as easily ask, since the government is using force to collect taxes to provision itself, why can’t it just collect commodity money like gold with a tax, and then spend that gold to acquire its necessary provisions? "

Because that commodity then first has to exist, and sometimes it doesn't - as the 'specie shortage' period in England in the 17th Century that brought the 'free minting' period to a close, and created the Bank of England shows. [0]

Why bother, when splitting twigs in half, or indenting a receipt on paper achieves the same ends at much lower cost?

What makes fiat currency work is that nobody else can issue the unit of account that the central authority requires in settlement of taxes. Anybody who does is jailed. Anybody who fails to pay is jailed and has their assets confiscated.

Since the central authority arises from the organisation of the population as a group, it has the political and physical power to enforce the tax on everybody who wants the protection of that group. Anybody who doesn't is 'outlawed' in one way or another - which is effectively a death sentence.

[0] "Money, Politics and Power", Richard A Kleer: https://amzn.to/3tHSRto