Cryptocurrencies like bitcoin are very unpredictable. "UBS", an investment bank said that it is "highly doubtful" that these will ever become conventional currencies. "The need for companies and individuals to pay tax receipts in government-issued currency, and the potentially unlimited crypto-money supply, pose significant barriers to widespread adoption".
Volatility strips bitcoin of the characteristics needed of a credible substitute currency, making it instead a speculative asset, a get-rich quick scheme.