A straw man for what? Once your net worth reaches a certain level, it would be silly to let it sit in any one asset, whether that's a specific currency or commodity or whatever.

Diversifying with a deflationary asset like Bitcoin is a wise strategy, one that is likely responsible for its $160B market cap.

People who have surplus wealth usually have a mix of assets - stocks, bonds, commodoties, cash, property, and sometimes more exotic assets like art, collectible cars, cryptocurrencies, whatever. Everyone has their own preferences and risk appetite and as such a different mix of assets.

Cash (at least major currencies) is one asset class that is relatively safe but tends to depreciate due to inflation, especially due to recent monetary expansion by central banks. Cash can also be easily seized, and this is a cause of concern for some.

Contrasted with other asset classes that have yield, having all your net worth in cash would not be something you want to do.