I can guarantee you if everyone tried to get cash for what they have in the bank. It is not there. They could never print enough. Most money is out in cyberspace. Cash is Cash.
Get Cash?
Are you talking about paper money?
Of course they don’t keep that much on hand in the bank, but paper money is easily printed and cheap. The issue is purchasing power and “trust”, however miss-placed.
Gold always has a value, but most people will not accept Gold for payment of a bill, there is no immediate mechanism to convert it to something they run through their accounting system.