My mother, a careful shopper, rarely misses a chance to use loyalty cards at her favorite establishments. Several years ago, as a checkout clerk was stamping her Subway Sub Card club (buy 8 six-inch subs, get the ninth one free), I asked her: “Does this loyalty club make you patronize Subway more often?” After a moment of reflection, my mother responded with a knowing smile: “No, but it is nice of them to offer it.”