Bitcoin is an alternative currency, it was not meant to replace fiat currency unless the value of a country's currency drops, then the citizens are free to switch to bitcoin as the primary means of payment but not an option for a country. We have seen the economy of Venezuela collapse which cause the bolivar value depreciate, but the government didn't adopt bitcoin to replace their bolivar, instead created their own crypto called petro coin that launched in February 2018. There some several flaws in bitcoin, but the main quandary is the volatility which may make people hesitate to use it as a major currency on a daily basis.