Trend . . . ?
More a fad than a trend, and basically much ado about nothing.
As Robert states, "A currency can’t simultaneously be a medium of exchange for commodities, and a commodity itself." That smacks of using salt for currency. In some places, perhaps valuable. In others, not at all. A later, better system was the barter, where one actually traded all goods owned, many usable and others not so much so, and made the best deal possible.
Don't burn all your money just yet.