There are a million ways you can hide information securely (like a private key), and it's far easier than hiding gold. And only an idiot would keep a cryptocoin wallet on 1 computer with no backup.

You put your money in a bank and it's no longer your money. Trust me, I had my main bank account locked up for an entire month due merely to (groundless) suspicion (basically, I made too much legitimate money too quickly (!!)). And then, Simple.com closed my account without warning, apparently due to violating TOS by not using it for "personal use only", which was total bullshit (messing up payments in transit AND not getting back to me for DAYS about where the hell they put my money: https://twitter.com/pmarreck/status/739994477339758592)!! Don't think for ONE SECOND that your bank money and your credit will always be accessible to you (not to mention fraud, identity theft, and other things that are not possible with cryptocurrencies). There're plenty of cases of some government dipping into accounts and helping themselves. If you think your money is safer in a bank than in a properly-secured private key, you're pretty naïve.

At least in the US, the worst case is a temporary lockup like you described. Banks are limited in how long they can hold your money. If your money is in a bank, it is guaranteed from fraud and theft.

You can't say that about Bitcoin. Add to that the fact that if you want to use Bitcoin to buy most anything you are going to have to either rely on a bank to handle transfers or find someone on the street with cash to buy the Bitcoin (dangerous with no guarantees).

I'm totally I'm unconvinced that you're offering a better alternative.

If you lose a key then that's it you're done forever. With banks you had hassles but clearly you got your money back. I have a hard time believing a billionaire wouldnt also be able to get their money back from the bank.