I think the only reason why money is currency is out of the public consensus, which is we need it. When something is widely acknowledged, it builts its own power to convert messages. Gold and silver are once the currency in circulation, however, no matter how much value they possessed, they are eliminated by times from being used as currency. That is how things go all the time, and same as currency. The appearance of Bitcoin fully shows implied that the need for some cryptocurrencies is inevitable. And seeing through those years, though many bumps in the road, it is thriving from an overall view. And it will definately keep this trend in future. Though Bitcoin is not like gold or silver in the way of possessing value, it has value for sure. And the value possessed by Bitcoin will definately go up as the Growing of public consensus.