Bingo
"It also has a long history as a medium of exchange. I am told that makes it ideal as money (let’s face it, barter can be very cumbersome)."
A barter economy would never have developed even the feeble economic systems of early civilization much less modern society. Thus the advent of the medium of money. And yes perception of value is of course fundamental to demand, whether gold of silver or gems or paper money or electronic money or WHATEVER.
Certainly if civilization collapsed a la The Walking Dead then almost only necessities would have value.