What should we use as an exchange? Food? Please don’t say gold. Gold is not worth anything either, just what people think it’s worth. You could make this argument about everything. Do you think we should barter and trade everything we do?
Think of it this way. If you were selling, say, a car, and someone gave you 200 one hundred dollar bills for it. Now, what can you do with those 200 pieces of paper? I guess help pay off your mortgage, or something like that. It's only good for anything if it is commonly accepted. But there is no real logical reason to accept it.
Until last century, we basically had a modified barter system. Our money represented actual tangible items. A bill represented a share of some item, like x number shares of stock represents ownership of y percent of company z.
When desperate times come, our economic system will collapse, when having cash (or mere bits of data) will not help you get food, water, shelter, etc.
What could be base our currency on instead? Well, land wouldn't be a bad idea. Engery reserves wouldn't be bad at all, either. I don't quite know. But I do know our current system is not as stable as it appears.