Bitcoins have three useful qualities in a currency, according to The Economist in January 2015: they are "hard to earn, limited in supply and easy to verify". Economists define money as a store of value, a medium of exchange and a unit of account, and agree that bitcoin has some way to go to meet all these criteria.
Bitcoin is very good and we all love t due to how it is; from being easy for making transaction, not being manipulated by the government and also having to pay lesser fees for the transactions you carry, thats really cool. But, I have once been in a conversation and the conclusion we came to was that Bitcoin becoming the world currency might be disastrous for the economy. Fiat might not be something we like due to several reasons from being controlled by the government and other reasons, but still it has features that makes it seem better.
According to a research, most of the Bitcoin transaction is by people who are using it for illegal purposes, and by doing so they are able to hide from the government. The Bitcoin system cant be controlled by the Central bank as they do with fiat, that means theres no way to deal with financial crisis, manage business cycle, etc.