You want to own something? You need to be capable of keeping it safe. If not entrust it to someone who is and hope they don't steal it.
The same goes for everything in life.
The fiat banking system has demonstrated what it does when we trust it with our fiat money. It steals it (through zero-reserve banking aka infinite debasement).
With bitcoin I can audit the wallet they hold for me at any time (public keys) and know that they can't debase it.
