Bitcoin only economy will be very volatile in nature. Also Bitcoin network cannot sustain the transaction volume of a country. So you will probably have to pay a huge amount of transaction fees for every payment you make. So Bitcoin only economy is not sustainable and not practical.

Bitcoin was never created to replace the current economy or the banking system. It had created to remain as a parallel economy and that's exactly why it thrived this far. We surely yl do not want Bitcoin to be controlled by the governments and corporates.