Well, it does. A ounce of 92 percent gold is always a ounce of 92 percent gold. So, at least one part, one variable is fixed, making calculations of the possible values of other things less opaque. But, by and large governments don’t care for clarity. Illuminates, a bit, all sorts of activities.
In that case, a $1 FRN is always a $1 FRN.
So, at least one part, one variable is fixed
If it doesn't keep prices fixed, what is it good for?