Because complaints to the grocery store have not brought about action. The grocery store has ignored the complaints and the produce is still not fresh enough. Going to the hardware store and everyone else in town will start a rumor and bring about attention to the lousy produce at the grocery store. Eventually the grocery store will learn about the rumor and start worrying about the implications of so many people being upset with the produce and looking for alternate ways to obtain produce. They will not want customers going to another grocery store for produce because they know other products will be bought while they are there.