A medium of exchange is an intermediary instrument used to facilitate the sale, purchase or trade of goods between parties. For an instrument to function as a medium of exchange, it must represent a standard of value accepted by all parties. In modern economies, the medium of exchange is currency.

Standard of value is antithetical to "change", standard is by the very definition means NOT CHANGING.

If money changes wanton in how much value it measures it's not standard.

For money to be both a measure of value and a STORE of value, it creates a contradiction in function. A unit is an abstract idea, not a tangible thing.

For example, a meter, a ounce, a second, are all abstract ideas that are never tangible, cannot be by their very function of Measurement.

You cannot own, transfer or touch a kilometer, nor a second, nor a measure of value. You can use a length of rope to measure a kilometer, but that doesn't mean that the rope is a unit of measurement, the unit is abstract, everyone can create them and the standard is hammers down in stone and unchanging, or it will invalidate all other measurements.

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