In part of a long essay economist Nouriel Roubini writes:
[C]ryptocurrencies in general are based on a false premise. According to its promoters, bitcoin has a steady-state supply of 21 million units, so it cannot be debased like fiat currencies. But that claim is clearly fraudulent, considering that it has already forked off into three branches: bitcoin cash, litecoin, and bitcoin gold. Besides, hundreds of other cryptocurrencies are invented every day, alongside scams known as “initial coin offerings,” which are mostly designed to skirt securities laws. So “stable” cryptos are creating money supply and debasing it at a much faster pace than any major central bank ever has.
As is typical of a financial bubble, investors are buying cryptocurrencies not to use in transactions, but because they expect them to increase in value. Indeed, if someone actually wanted to use bitcoin, they would have a hard time doing so. It is so energy-intensive (and thus environmentally toxic) to produce, and carries such high transaction costs, that even bitcoin conferences do not accept it as a valid form of payment…
Since the invention of money thousands of years ago, there has never been a monetary system with hundreds of different currencies operating alongside one another. The entire point of money is that it allows parties to transact without having to barter. But for money to have value, and to generate economies of scale, only so many currencies can operate at the same time.
In the US, the reason we do not use euros or yen in addition to dollars is obvious: doing so would be pointless, and it would make the economy far less efficient. The idea that hundreds of cryptocurrencies could viably operate together not only contradicts the very concept of money; it is utterly idiotic.