I know there's at least one cattle ranch taking coin. So.... supply and demand. If there should eventually be a significant number of food trucks taking bitcoin, it's more likely their suppliers will. It all snowballs, or branches out... whatever you want to call it. Customers service end-business which takes coin, ranch services end-business, farm services ranch, and now the bakery has the option of a supplier taking coin, too. Assuming the end-business isn't immediately converting coin, they may be particularly interested in being able to buy their needed supplies for coin - in which case, more BTC customers = more coin = higher likelihood of trying to find suppliers taking BTC.