And the reason it is fungible is that it has the backing of the US Government, US Treasury and Federal Reserve. People might not 'care' about the govenement wh

And the reason it is fungible is that it has the backing of the US Government, US Treasury and Federal Reserve. People might not 'care' about the govenement when they use cash, but try and pay with something that doesnt have some backing - say for example small rocks. They too are fungible, you can buy bags of them at any good hardware store. They are decentralised, trustless, effectively untraceable and could in theory be exchanged for goods and services, if both parties were willing.