The short answer is, fiat currencies are purposefully inflationary
The long answer is that Bitcoin has been made deflationary, due to a hard cap, coin loss, hoarding, or whatever. In the view of Gresham's Law, Bitcoin is good money to be stashed away, while fiat is bad money to be spent shortly. So whenever there is a choice to be made between what to spend and what to save, the choice is evident and straightforward, so there is no need to name it here
That's correct, except that we cannot apply Gresham's Law to Bitcoin. It only works with commodity money and only given that the price of both good and bad money is set exogenously. In our situation Thiers' law is more appropriate, which states the opposite to Gresham's Law
We already discussed this matter in the past (
here, for your reading pleasure)
And someone has come up with exactly the same reason, namely, Thiers' Law. However, Gresham's Law, or its extension, still persists if we consider two currencies, which are freely exchanged into each other at market rates. Thiers' Law basically describes a situation when one currency fails as money, i.e. no one wants to accept it. In that case people simply refuse to transact in it, and thus no free exchange is possible. Obviously, this is not the case here. Bitcoin is a worthy speculative asset, and it is not a good idea overall to spend your capital on everyday needs, Gresham's Law or otherwise