We did. Constitutionally, the dollar was based on silver & gold. Then Nixon decided to steal a lotta billions of dollars in gold/silver by "going off the gold standard" - to wit: the IOU dollars were disowned. The worth-the-paper-it's-printed-on dollar has been collapsing ever since.
The decline and fall of the gold standard is a sad tale indeed. The problem is, the genie is out of the bottle and no government wants to give up the ability to manipulate the money supply.
Anyway, the wall street festivities start now.