Each banking system has its advantages. The advantage of decentralized banking is that you are the only one under the control of your keys, as stated by OP, so theoretically nobody can touch it, besides you.
However, in case you have your wallet hacked and funds are lost, it will be much harder and even impossible to retrieve it, while at centralized banking system, transactions are reversible and you can count with the help of bank managers to track your money and rescue it back to your account. On the other hand, if a superior order comes from the government seizing funds, even the managers won't be able to help you keeping your money in your hands, as they will comply with requirements from their superiors.
You have to measure the pros and cons of each system and make your choice based on your analysis.
Truly, both have pros and cons and sometimes even crypto users can't avoid the use of banking system.
If you have mortgage, more than likely, you need a bank account as it is a requirement for this transaction to push thru.
But if you feel you have nothing to do with banks, and just use crypto or btc to go on with your life, why not?
Remember, each one of us has own priorities, so it depends on us if we do need bank or btc only or both.