In a way, this is true which makes currencies having bad monetary policy a danger to the economy. But well managed government currencies are designed to curtail

In a way, this is true which makes currencies having bad monetary policy a danger to the economy. But well managed government currencies are designed to curtail the "ponzi" aspect to them. They do this by insuring the currency loses value with time which prevents hoarding and by varying the supply and interest rates to make sure the currency is never too strong a competitor to real business investment. You don't want create a too compelling intrinsically valueless alternative to investment into real production and real economic activity because this jams the real investment markets. Currencies that are not designed to lose value over time can never be stable. Intrinsically worthless tokens engineered to have better than market risk adjusted, liquidity adjusted, real returns compared to real productive investment will always be unstable and fluctuate increasingly wildly as they get more popular. This is a result of physical limits of production. As people hoard worthless tokens, their price increases which causes more people to hoard them instead of investing in real businesses with real production capacity. This eventually causes production capacity to drop. That's right, when enough people do it, token hoarding displaces investment in businesses and factories and lowers global production capacity. This means token hoarding causes a drop in things available to buy with these tokens. Eventually there will be people who want to buy real things with their stock of tokens. The tokens will be chasing fewer goods which means prices for stuff will rise (tokens will lose value). This might happen suddenly when people with large stockpiles of tokens notice that value is dropping and that there are tons of other tokens waiting on the sideline to make it drop even further. Hoarders might rush to get rid of their stockpile all at the same time before they're worthless which will cause their fall to worthlessness. This drop will bring the tokens closer to their natural intrinsic value of zero. The cycle can then start again, such is aggregate economics. The 1920s and 1930s suffered from this type of cycle but with gold tied currencies instead of cryptocoins. It happened to a lesser extent in 2007 when western world central banks failed to keep inflation rates high enough. It's important for the world's sake to not let deflationary currencies become too popular. When savings or financial promises are insufficiently tied to future production or to accumulation of real goods, there will be disappointment when a lot of people try to exchange them for real stuff. That is true for crypto currencies as well as government currencies (that is why the system is designed to make banks invest people's money in real businesses and minimize the proportion of money that is stockpiled idly).