National currencies are backed by government bonds, while Bitcoin is commodity-like, in that it’s not backed by anything — it’s a monetary unit in its own right. This avoids the recursive relationship between national currency and the government bond, which exists because government bonds are denominated in the very currency whose backing is that bond. So currency is valuable because it’s backed by bonds, which are valuable because they’re denominated in that currency, which is valuable because it’s backed by bonds... etc.

The problem with a currency backed by bonds is that the value of a bond depends on the rate of interest which, in turn, means that the value of the currency depends on the rate of interest. Traditionally, bonds were denominated in gold, which avoids the recursive definition of the value of money, because it ensures that the value of the monetary unit does not depend on the prevailing (bond) interest rate.