Did you ever walk into a hardware store or look at a Grainger catalog and wonder why there was so much stuff?
Bartering would be impossible today. How would you find the guy that has the drill bits you need and is willing to take your beaver furs from you...Grainger has no need for corn.
So a common form of currency becomes the standard. It's something everyone wants because everyone else will accept it as payment. Prior to the 70's the standard was gold. Now, money isn't worth the paper it's printed on and coins have very little if any actual precious metal.
The indians actually did have forms of currency. They would carry specific types of shells that were useful for making fishhooks(functional for most tribes) and carving into beads(aesthetically pleasing as well as a show of wealth and therefore power). These had a common value, as did obsidian and flint for tools, and sharp points for spears and bolts. The items were typically small and lightweight so they could be easily transported.
https://quatr.us/nativeamerican/earl...ming-trade.htm