Well I think that's kind of my point. When we talk about money we're using a modern mindset that doesn't fit a primative economy.
You could say there are three stages an economy can go through. (I'm making my own terms up by the way):
Stage One - Barter Economy: I will swap you a valuable item I have that you need (food say) for a valuable item that you have that I need (some cloth say). The problem with a barter economy is that it isn't very liquid in that it relies of me finding someone who has what I need who also happens to need what I've got.
Stage Two - Coin Economy: We will agree to use a particular portable and long-lasting substance whose quantity available is reasonably fixed as a standard item to barter. Gold, say. So I can swap my food for some gold you have and then later swap some gold for some cloth. This removes the need to pair up producers. However, it only works if I'm happy to swap gold for food today knowing that my gold won't be halved in price by tomorrow.
Stage Three - Money Economy: Now we agree to have a concept of money, represented by abstract tokens. I'm happy to swap my food for some otherwise meaningless bits of paper because I have enough faith in the future of civilisation (i.e. the government and the rule of law) to believe that tomorrow I will be able to swap those bits of paper for some cloth.
The key thing here being that a government can't just print more gold. Gold's rarity is intrinsic; it would stay rare even if the government fell and anarchy reigned. Whereas the paper currency would then be nothing more than arse-wiping material.
Nice to know I'm not the only one.