Multiple Uses

Elves draw magical power from the number of trees that exist within a certain range. Humans in the nearby town want wood for housing. This is conflict. Economies can drive conflicts. Conflicts can also drive economies. Dwarfs need elf skins to enchant their forges.

Conflict like this is good for gameplay (if not overdone), and having multiple uses for resources is a neat way to introduce it. The same technique can be used to enhance trade (by driving up volumes) and challenge monopolies (because the opposition to them will be greater).

Similarly, having multiple resources for the same use ¹ can keep a virtual economy from being mugged. In practice, goods are usually implemented as being similar but not exactly equivalent, so a snow wolf pelt might have a slightly higher warmth factor than a snow bear pelt, but get mangy quicker. Nevertheless, if there were a sudden shortage of snow wolf pelts, people who made clothes out of them ² could switch to bear pelts. When people have choices like this, meaningful decisions must be made; meaningful decisions are at the heart of gameplay.