Whole Foods is enjoying the fruits of its marketing labor these days, but its long-term success may rely more on its affinity for workers than affinity with shoppers. Until 2014, Whole Foods had not so much as tested a customer-rewards program because it likely didn’t see the need to. Its shoppers sought out its stores for the quality of its natural products as well as for the amiable, knowledgeable staff – not for discounts. But with the September launch of a pilot affinity (loyalty) program, called Whole Foods Market Whole Foods Market Rewards, as well as efforts to stock the shelve...