Because having a single common unit of measure, medium of exchange, and store of value, is of immense utility in smoothing out global trade. When you index the cost of everything against a single common denominator, you dramatically reduce exchange rate and credit risk, and you bolster the trustworthiness of your goods and services, because the currency you are using, has a universally trusted backstop.

Of course, the fatal flaw in this rather happy state of affairs is that the people who maintain this reserve currency, must themselves be trustworthy. If they are not – and the US Federal Reserve most assuredly is not – then the global reserve currency will serve to export inflation and destroy value around the world.

Historically, gold coins have been used as that common medium of exchange – no matter who issues those coins, the weight of gold in the coinage determines its value. The problem with gold is, of course, that you have to carry it physically. But I see no reason why tokenised gold, using a digital wrapper around the actual physical commodity, could not serve a similar purpose, albeit on a limited scale given the constrained global gold supply.