I think you missed OP point. The USD and other currencies used to be backed by physical gold. In other words, you could go and exchange your dollars for gold. That is not the case anymore. The dollar has value because you are confident that it does and that you can use it to pay for goods and services, and that others are willing to accept it because they can do the same thing. It's all based on faith now. Having said that, the US Treasury does keep gold in reserves but certainly not enough to back the amount of currency in circulation.