Before something can be a store of value, it needs to have value. Gold gained this initially through being wanted for use in jewelry. The only way bitcoin can gain value, is by proving its worth as a useful (or even best) means of electronic payment.
This is a good point. Can bitcoin be a reliable store of value (as it currently is) without being supported by its use as a highly convenient electronic payment method? Can something be established solely as a store of value? Where does the value come from? I'm guessing it being a highly convenient store of value... But I can't wrap my head around it to be convinced that it can be enough...