"Currency's primary function is the store and transfer of value. "

Almost, but no cigar. Currency's ONLY function is to represent transferrable value. To serve that purpose, it must store value just well enough, viz., long enough for the value it represents to be transferred. If an asset stores value any longer, and especially if it appreciates, it won't be transferred - people will hoard it - and its function as currency, will not be served. Such an asset isn't currency.

Point is, "currency" is a label attached to something on the basis of what it does, not on the basis of what its inventor hopes it will do. A concrete life preserver is NOT a life preserver. It is a piece of rock that some moron THOUGHT could be used as a life preserver. It is in that sense that Bitcoin is not currency. Bitcoin can be used to transfer value, but it does so in the way sending money by wire does it. The electrons are not currency, and neither is Bitcoin which is essentially a modem - it turns fiat into something that can streamed and then turns the thing that is streamed back into fiat.