Independent currencies don't have that particular source of demand, but economies are made of much more than tax debts. And you could argue that overbearing policy itself creates demand for currencies that enable untaxable (and other illicit) transactions. Government itself could be said to encourage demand for both forms of currency.

I doubt that the 'neat technology' aspect contributes much to the exchange rate; or little more impact than coin and banknote collectors have on mainstream currencies. You don't need to put much money in, or participate in many transactions, in order to examine the technology itself.