Banks aren't good! therefore cryptocurrency was created, but there are only a few that have good value, indeed decentralization is a good system for the future, but for now if the BANK ends, the world will be shaken
With your theory how you will be purchasing bitcoin, barter system or you will be using the banking system and fiat currency to purchase the coins, if not how you are going to invest in bitcoin to begin, i do not understand from where you get these ideas that banking sector will be replaced with the introduction of virtual currencies 
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