[jbotz]

There is one thing that's absolutely guaranteed about paper money... you'll be able to pay your taxes with it. I'm not being flippant here, some people, like the MMT (modern monetary theory) crowd, are saying that's the whole basis of fiat currency.

[pydry]

There's interestingly a couple of instances where governments have collapsed and the currency was still traded (Somalia, Kuwait).

There's definitely an element of "it's valuable because people think it's valuable". This might be working to Bitcoin's advantage.