well 
for one

the main thing that makes the USD different is that it is the *most saleable good*. accepted practically anywhere.

that is another of the primary characteristics that makes it "money"
and bottles of water are not because they are only salable based in their utility

that is why prices are *accounted* in USD. and not something else.

so
while i see your point
it doesn't really express the reality of the situation

people *account* in USD *units* because it is universally saleable.

that is just how the world is
not saying it *should* be this way
but its a fact.