Haha, finally. Some people stay up nights contemplating the universe, I think about concepts such as wealth and value.
As a people, we give value to objects based on their rarity and the amount of work needed to produce or acquire them. For anything we give, we feel we must receive equal compensation, which makes sense; we had to work for it, why should he get it for free. Originally, that need for compensation was satisfied by the bartering system. In time, currency replaced that system and aided greatly in international trade.
We use currency as a physical representation of the value of certain goods and services and no matter how we might try, people need to apply value to these objects and deeds. Completely removing that system of value is something far to radical for people to even consider. It would be a paradigm shift of the highest magnitude. If nothing had worth, there would be no personal property. Stealing would no longer be criminal because you didn't lose anything of value.
Long story short (too late, I know), we need currency to fulfill our need for a concept of worth and value. Granted, the world might be better off without the concept of worth (at least for physical objects) but that's a topic for another thread, methinks.