What you are referring to as 'good money' , most people would call 'stupid money'.
It's a stupid idea to run a country with a fixed amount of currency - as the economy expands, more currency is needed - either that - or all prices of everything need to adjust because the 'stupid currency' is fixed.
A 'well managed' currency is better than a fixed supply.
Of course - the 'existential risk' is that some political cowboy will 'print money' for political reasons - this is the great problem that fiat always faces.
But this can be avoided.
Most major currencies are very well managed.
Also - remember that they are backed by actual assets - so money is not coming out of nowhere.
Almost all Euros are backed by some kind of quality asset. It's very rational to allow entities to 'trade' some kind of asset for currency at the central bank. This is actually more 'free market' than any kind of fixed currency.
National currencies - irrespective of the quality of their governance, fixed or not - are extremely useful to everyone. They 'spend' that currency because it's what's used to buy stuff.
Household expenditures: mortgage/rent, electricity, groceries, insurance, gas, car payments, cable/internet. Can you use BTC for any of that. Pragmatically - No. BTC is 'pragmatically worthless' to anyone - it has no reason to exist.
BTC is very useful to money launderers, tax evaders, and other people doing illicit things, it's a great currency for the black market. But beyond that, it serves no purpose. It's not a currency and it's a terrible store of value as compared to any of real-estate, gold, most commodities, a 'basked of bonds of equities' or a 'basket of currencies'.
It's a great intellectual exercise, and I think the 'paper value' of BTC will remain quite high for some time, but unless it sinks in as an actual currency of some economy (say, African nations where the currency is garbage), in the long-long-long run there's no reason for it to maintain it's value.