[remram]

From a global perspective maybe, from the spender's perspective any currency can only be spent once.

Whether you obtain a car by spending your bill or obtain gold by redeeming your bill... you gave your bill in exchange for the good.

[eru]

That's an interesting perspective to consider.

From an individuals perspective, there's a difference between letting my money sit under my mattress or letting it accumulate interest in an account.

I can only spend it once in the end, but the money did different things for me while I was still waiting and deciding.