What you are describing applies to all forms of money. It has value because people believe other people will use it as money. If that belief drops, the value drops.

People comment on gold and Bitcoin, but don't realize the same principles apply to US dollars and bonds.

> the same principles apply to US dollars

Currencies are a little different, since they are required to pay taxes; and payment of taxes is enforced (to varying degrees) by state violence.

Hence if you believe you will be taxed ("death and taxes" being the only certainties in life, etc.) then the currency associated with that tax has value, in that it avoids imprisonment, etc.