Many people argue that the presence of bitcoin becomes a threat banks, this is because by having bitcoin then we can do full control of all the money as happened with the bank.
There's nothing wrong with full control of your money. Banks were made in the ancient times, to save people's money. That time money was gold, and if you had a lot of money, it meant a heavy treasure chest, where you have stored your money. People put their money into banks in order to prevent it from being stolen by thieves. They had the chance to control all of their money, but the risk of the theft was really high, this is why they used banks.
In connection with bitcoin, this problem is solved by using cold or hardware wallets, they are small enough to hide it in your house. But, when you want to do a transaction, you have to somehow use your cold wallet or hardware wallet, and when you connect to the internet, your PC, tablet, etc. could be affected by a virus or malware, so maybe the next banks would be the wallet softwares (wallet websites), which ensure that your bitcoin in the wallet won't get hijacked during the transaction.