by Nicole Lane Erceg “Hi, are you a rewards member? If not, would you like to join to save 15% today?” It’s a common interaction between customer and checker. As more companies work to deepen the understanding of their shoppers and keep them coming back, reward programs have popped up in grocery stores and coffee shops, from online companies to bricks-and-mortar retail. Americans love them: 80% of adults in the U.S. belong to…