Banks are under control of government. So the very first reason is  privacy. Bank doesn't provide as much as privacy like bitcoin or any other decentralised currency. For any transaction you have to give your full information to the bank but in case of cryptocurrency that doesn't required. Transaction through bank are time taken and slow and some time their are so many paper work need for  a single transaction. Bank also charge high transaction cost for money transaction and because of these above things i don't like bank.