The real answer to the question "why banks don't like cryptocurrencies" is that they feel a certain threat. The growth of cryptocurrencies has surpassed all expectations, and this phenomenon is still very young, but it has the potential to shake the aging system.
Yes banks became afraid on it because bitcoin was very different compare to fiat currency. In addition the volatility of it was also a problem for them. Bank think that people will adopt it more. The decentralization of it was also one factor why banks are against on it because no one control its price even the government.