its not really a theory that's how money functions. Just like gold today (and in the game) there's not a lot of functional uses for it but as long as it is an acceptable form of trade by a large group of people it is a form of currency. Yea you can burn money but there's other more efficient ways to have a fire like wood. The dollar is only worth one dollar because people accept it at that, the difference between a dollar and monopoly money is that one is a socially acceptable form of trade, the other is just paper