Banks use tools as a store of value by holding some assets in reserves, for various economic benefits. Although, adopting Bitcoin in such capacity, would have it's pros and cons. Obviously like controlling inflationary trends, and even help stabilize the volatility of Bitcoin to its users, and conversely such volatility could also alter the stability of a banks statement of financial position. All these could add up to a more stable global economy. Surely banks have started to think of such prospect
Banks can do things they want even under regulations from governments and central banks as well as other regulatory agencies. They have never been a trustable and safe places for storing your fund especially in long term.
You mentioned about banks and their activities of using some tools for their benefits - which I think wealth growth potentiality. By chasing wealth, they take risk and they can use customer's funds deposited to their banks in shady, untransparent and also very risky ways. Customers can not know all activities behind the scene do by banks and they only know part of it when banks start death spirals or collapse.
It's super risky and to avoid such uncontrollable risks, you can store your property, wealth in Bitcoin. With Bitcoin, it's very easy and you can manage it all by choosing an open-source and non-custodial wallet for storing your bitcoin, having your own Bitcoin bank.
Events made you scare about custodial wallets, centralized exchanges.