I don’t think banks are the ones against Bitcoin. It should be the government that is against Bitcoin because they don’t have control over it. The banks actually report to the government and because Bitcoin isn’t doing the same, they don’t like it. Because starting from tax and other things they’d have implemented or rule they’d have set, they can’t. Bitcoin takes out the middle man and the government can’t do nothing about it, no matter much they dislike it.
Banks are against cryptocurrencies and Bitcoin adoption because if everybody switches to Bitcoin will the banks exist? Can you tell me that since the invention of Bitcoin that ain't there people who are no longer interested in keeping their money with the banks but rather prefer to use the money to buy Bitcoin and hold it instead of saving it with the bank.
Banks and the government works hand in hand so when we are saying anything concerning money the government and the banks are included because it's still same banks that keeps the income of workers and pays when the government gives an order and banks also generates revenue for the government so they are literally same people that doesn't want Bitcoin and other cryptocurrency to be adopted because since it's decentralized there would be no need for the government to seek for their percentage in transactions since they are not part of it but however, they can still tax centralized exchanges and other platforms used for p2p since they are converting their Bitcoin to the country's currency because the personal data they get from people for KYC verifications were being issued by the government.