Why everyone gets so surprised on this .. currencies are meant to provide credit, goodies and subsidies to its participants .. currency is valid and good as long as people belive in the ability of the issuer .. in this case USD cuz people belive in USA ; in case of Apple it is a $aapl and people buy aapl ( just as they buy TBills ) ;

Store of value ( Gold or BTC) on the other hand is something that is permission less and censor resistant. It stores "value" through real physical work commensurate to its value.

Currencies may or may not be pegged to store of values .. it's totally upto issuer and approved KYCed participants. For the record USD is the best currency out there . That said , currencies are by definition short lived because they are dependent on the health of their issuers ; whereas a store of value is for ever .. backward compatible .. because it has work built into it .