To count or seize the individuals cash, the government has to make some fuzz. Aka send men with guns.
There seems to be some divide in our world between people who consider individual power a good thing and people who consider it unnecessary.
Here in Europe, I have the feeling the vast majority of people consider it unnecessary. The vibe I get is "The system works, so why not let the government handle and control everything.".
I wouldn't be surprised if that is a global phenomena and holds steady throughout time. For example, even when the US government seized their citizens gold in 1933, there was no resistance.
That people consider "cash" something they "own" is already a sign that people don't understand and don't care how they are gamed by the government. The government can take the value out of that cash however it pleases by printing more of it.
And no matter how much the government does that, nobody complains:
https://fred.stlouisfed.org/series/BOGMBASE
Governments on the other hand understand very well that money is a sham. Thats why they hold hundreds of billions of dollars in gold:
https://www.madisontrust.com/information-center/which-world-...
Way more than they hold foreign currency.
Gold is hard to pay with though. When Russia had their Dollars frozen last year, it was not like they said "No prob, we'll use gold then". Therefore I wouldn't be surprised if countries will shift their reserves to Bitcoin in the coming decades. As it combines the durability of gold with the usability of money.