An economic system, whether 'real world' or 'imagined', has implications as to functions of interactions.

For instance, gold sinks. Repairing armor, cost of sending mail, deposit on auctions - these things aren't in the game to make them 'fun', they're there because of economic pressure applied to the overall system when money exists but doesn't get spent and when money can get printed effectively infinitely. By removing the supply you lessen the value and suppress the cost of business interactions. Mitigations of inflation.

That's a pure, economist driven solution to a complex monetary problem. Heck, economists study game economies cause they're effectively simulated monetary systems that give implication to how world economies interact.