It seems to me that you are confusing a decentralized cryptocurrency with a national digital currency) The national digital currency will not be subject to volatility and will be fully centralized. And this is the main goal for any government - control over its citizens.
That's right and compared to bitcoin or cryptocurrency, our fiat or national digital currency is more useful in terms of payment for the fact that it's faster and regulated at the same time, however, if people think of holding their fiat, then they should think wisely as we know how the government are handling our financial system, the economy is struggling and fiat's inflation will increase.