Fiat currencies are a means to do short term business. They are not useful as a long term value store.

If you have some wealth, it should be put in something which is independent of a currency, like real estate, stock etc. Of course this has it's own risks, but there nothing like 100% security.

OTOH: Fiat currencies are much more stable in the short term as any other means of parking value because they are stabilized against the market from the central banks. Unregulated systems like Bitcoin have much higher price fluctuations which makes them less predictable and thus much harder to to business with.