Fiat money is backed by nothing. Money backed by anything has more intrinsic value. Gold-backed currency has more intrinsic value than fiat currency. Gold is more valuable than nothing. I don't know if gold's the best basis for a currency but it's better than none. You're right in observing anything could be used for currency but wrong in thinking that something w/more applications, like farming equipment, should be used. The more ulterior/specific functions an item has the more its' value will fluctuate. Precious metals are rare and pretty. Folks won't change in their appreciation for shinyness as much as they will for food (which subdivides into types of food, methods of preparation, etc.) Gold has other uses so it might not be the best item for trade but it's better than farming equipment which's inherently tied to farming, fuel, machinery manufacturing, etc. so it'll be worth more to agriculture markets than the overall market. It's also desirable that a trade-standard be easier to repossess than the things it's traded for. Even the lightest farming equipments, like a pitchfork, is bulkier than a gold coin.
