"Can't walk around with gold in your pocket." That's a very narrow way of looking at things.
Imagine a world where everything is valued in gold, or perhaps gold and silver.
Right now that would mean one gram of gold = $40.72 €=36.36 Yen=4,471.71
and so on.
Imagine a reputable blockchain service that allowed you to transfer payments in grams of gold and fractions there of, and also offered a debit card. You could opt to store your gold there, or simply load a debit car at a service center similar to a FX exchange buro that you see in places like Amsterdam.
Quickly you would begin to think of prices in terms of grams of gold.
Your hotel room in Rome might cost 3.8grams. A coffee 0.1grams etc.
There could be universal silver coins that you could buy with your debit card for small incidentals purposes.
There is no more printing paper currency. After hundreds of years we would have actual real money. Universal, with intrinsic value, joined with blockchain technology for transfer purposes.
Sorry, I'm not with Andy on this one, I'm with Jim Willie -- not to imply Jim would necessarily agree with how I framed this.