Fiat currency is and always has been a tax prepayment - whoever issues it (whether public or private) - and it is irrelevant how many units of it I hold, although historically I would have expected some sort of return to be convinced to do so.

The return is the opportunity cost of not having any on hand, which is substantial, either because of fines incurred for tax nonpayment, or the need to pay interest on borrowed money if everyday counterparties demand cash payments.

Finance is the brain [tumour] of the economy