Bitcoin, which began as a tool to carry out money transactions that were difficult if not impossible to trace has morphed into a gambling medium. There is nothing behind it other than supply and demand. And the demand now comes mostly from perceived riches. If the perception fades, so too will demand. It is that simple. You have Bingo and you have Bitcoin; the risk to reward ratio is similar for both.
You can buy things with both bitcoin and sovereign, fiat money, and you can gamble with both. But these are about the only similarities. Fiat money trades relative to other fiat money, according to supply and demand, but it doesn't float entirely free on open markets because issuing governments may intervene in markets to stabilize their fiat issue as they deem desirable.
Fiat money is here to stay as it is by far the most practical and flexible of all sovereign money's yet devised. Basing a sovereign money on a rare commodity is a ridiculous idea bound to fail. The only reason it worked in the past is that people* hadn't realized how utterly ridiculous commodity based money really is. Once the absurdity and non-sustainability of commodity-based money was recognized it quickly disappeared in favor of much more sensible fiat money.
Fiat money ultimately takes its value from the issuer's authority to tax**, the issuing nation's productivity, the amount of fiat in circulation and the public's perception of these factors. Reserve, fiat money also derives stability from large pools of reserve-currency-denominated assets in the hands of non-issuers.
These highly desirable features are absent from crypto currencies. This is the reason that any nation foolish enough to adopt a crypto currency as a national unit of account will very quickly revert back to the use of either their own or another nations sovereign fiat currency. No nation, however, will adopt another nation's fiat currency unless circumstances force it to do so. ***
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*Some of course did recognize the absurdity of basing a national currency on a particular commodity, but their arguments were unpersuasive until crisis, easily enough predicted, forced recognition.
**This is the critical factor that must be present, because no country that issues its own fiat currency will accept any other currency in payment of taxes.
***In the EU monetary Union we have an example of what were independent countries voluntarily giving up absolute sovereignty over the currency they use in favor of joint sovereignty among several States and without adopting a universal Euro Bond. (Germany has consistently opposed the Euro bond.) Thus the States of the Euro monetary union have accepted an incomplete union by voluntarily ceding control of their currency to a collective without a common bond. This has caused no end of difficulties for the union, and may ultimately cause its dissolution. Many of these problems can be traced back to long held anachronistic beliefs about money that no longer make sense.