To summarise: There is a social demand, even pressure, for a medium of exchange whose use value is not that it can be planted and harvested, milked or consumed, but rather that it acts as a kind of buffer against the complication of wants remaining unsatisfied due to a mistiming in the availability of such goods to be exchanged. The medium of exchange isn’t completely arbitrary, it has to have certain key properties in order to be fit for purpose, and it may be that a change in the marketplace transforms the medium of exchange into something more applicable. It may be that gold, for example, starts to lose its lustre as a convenient medium of exchange in favour of something more pragmatic and suited to a changing infrastructure.