The coin of the realm for the United States of America, is its Federal Reserve note, colloquially known as the dollar bill, of which, this currency has degraded over time into becoming just a fiat currency. In other words, there isn't anything backing the dollar bills in existence other than the trust that people and institutions place into it, as well as the inherent backing by "the full faith and credit" of the United States government. Not too surprisingly, fiat currencies, have a very strong tendency to become less valued over time, which is why today's dollar bill does not have even close to the value of its predecessor dollar bill, that was previously part of the gold standard, and was severed from such in 1971. So that as of 2020, it takes as reported by dollartimes.com, $6.46 to equate to what the value of a $1.00 was back in 1971. This so indicates, that those that hide their money under their mattress, or fall asleep, akin to a Rip Van Winkle with money in their pocket, are not going to be too happy, upon their realization that dollars do not well hold their value over time.
The fact that the United States government essentially monopolizes what is made to be currency in this country puts them in the catbird seat of utilizing that currency for the primary benefit of those that are knowable about future interest rates, the velocity of that money in circulation, and the strength of that currency vis-a-vis other global currencies, of which that knowledge materially benefits those that know of these things, in the sense of being able to profit immensely from it. Further to the point, those institutions which are aware that a given currency is going to be, for instance, devalued in comparison to a basket of other currencies or to a particular currency, are in the commanding position to profit, handsomely from that knowledge. This so indicates that when it comes to the coin of the realm, that a given country's currency is far too valuable of a commodity for those that should not know, which are typically considered to be the general public, what those that are the arbiters of that money do know, beforehand. In other words, those that control or have massive influence upon the issuance and value of money have zero interest in fairly sharing that wealth or being fair with the general public when it comes to that money, because part of the way that they maintain their power, influence, and wealth is by gaming the system, so that they thereby receive unearned riches from their inside access to all that is pertinent in regards to that currency.
So then, in a construct in which the general public must out of necessity utilize the coin of the realm for all of their transactions, they are perpetually in a very vulnerable position to having that which they have so long worked and labored for, becoming devalued, literally overnight, and thereby what would appeared to have been so secure, actually becomes not. This signifies that fiat currencies are an ever present danger to the general public and to the degree that the general public can mitigate such, by thereby storing their wealth into things that are tangible and have a strong tendency to hold their value, such as land, real estate, equipment, and precious metals, they should prudently consider doing exactly that.