Now you're talking about foreign currencies. Yes, foreign currencies can be traded for speculation purposes. When a speculator invests in a foreign currency, they think that the currency will appreciate in the future. The important fact is that currencies appreciate and depreciate according to international trade and a whole bunch of other factors unrelated to speculation. The speculator does not rely on other speculators buying the currency for it to appreciate and making a profit. Therefore, speculation with foreign currencies is not a pyramid scheme. This is in stark contrast with crypto-coins, because unlike the demand for foreign currencies the demand for crypto-coins is mainly fuelled by speculation. The only non-speculative uses of crypto-coins (as far as I know, ransom payments and purchasing of illegal substances) constitute a tiny minority of the trading volume. Therefore a crypto-coin investor absolutely depends on other "fools" investing in crypto-coins at some later time in order to make profit. This is confirmed by the fact that they're constantly trying to talk other people into buying crypto-coins, which is never the case with fx speculators. When they run out fools, they will no longer be able to make a profit. And this is why crypt-coins are a pyramid scheme and international currencies are not.