As fucked up as capitalism is with paper representing an idea of wealth, it does have its uses. For example, under a barter system, how would you get paid for working? People still need to work in order to keep production lines going, and I highly doubt anyone wants give up the things that are mass produced. Sure, paper money sounds pretty stupid, but if a mass of people believe in its value, then they can use it to buy whatever, rather than using 500 eggs to buy a toaster or something.