The fact that this parent has a number of children that don't seem to pick up on this is problematic to say the least.
Neither of them have to be. All exchanges take place in pairs; one holding is exchanged for another. Buying BTC with dollars is (USD, BTC); buying Microsoft is (MSFT, USD); buying EUR with dollars is (EUR, USD).
Nothing prevents you from pricing Microsoft stock in BTC or BTC in EUR or Etherium.
The holding as such, however, is only a fiat holding when it is in fact either a (wad of) cash equivalents and/ or a bank balance.
There isn't a person on earth for which there is only two types of relevant holdings, in either USD or BTC. A person that (seriously) considers acquiring a crypto holding, such as BTC, is most likely choosing between other crypto currencies, gold or silver, primarily. Even more likely, they're merely FOMO-speculating as a complement to plain stock holdings.
The fact that a number of you don't seem to understand this should call your competency into question.
But yes, I agree with you about where fiat is used. It's almost always used by people that don't quite undersand the concept of value or that of money for that matter.
Money is not declared valuable by political authority. That is just not how it works. Crypto is what's declared valuable by fiat, ironically. Its value is described as derived in terms of a limited supply (it's just like Gold!)
Fiat currency derives its value from network effects, debts and the feeling of safety (or the lack thereof.)
There is plenty of evidence to the contrary.