Its a self reinforcing negative feedback loop, which I realize is a redundant way to say it. By keeping gold with a custodian, they reduce the usefulness of gold as money. As currency continues to debase, proxy stores of value like houses go further to unrealistic prices. As fewer people are able to own things, they live by the permission of the centralized system, and feel insufficiently secure to protect their property themselves. And back to custodians, and repeat. Bitcoin must avoid this at all costs. Stuff like ecash make me worry.