The difference is that the local monopoly on violence forces demand for their fiat on the people and organizations within their sphere of influence, explicitly and implicitly.
It remains to be seen if an entirely voluntary money can be a major player in the modern world.
Then again, raw fiat is a very new experiment as well. It's only been about 50 years since the US broke the pretense of the dollar being constrained by gold reserves. So from that context, bitcoin's 13 years doesn't actually seem that radically young, especially if compared to gold's 5000 years.
It remains to be seen if an entirely voluntary money can be a major player in the modern world.
Then again, raw fiat is a very new experiment as well. It's only been about 50 years since the US broke the pretense of the dollar being constrained by gold reserves. So from that context, bitcoin's 13 years doesn't actually seem that radically young, especially if compared to gold's 5000 years.