To shore up its lagging business, restaurant chain Denny’s ran an ad during this year’s Super Bowl promising a free breakfast the following Tuesday. A whopping 2 million patrons showed up for their Grand Slam meals. On April 8, they’re back again with a “bring a friend, get a free Grand Slamwich” offer. From a marketing perspective, these are great ideas. The Denny’s brand has gotten “soft” over the past few years and needed to reacquaint consumers with their offerings. By all measures, that objective has been met.

But Denny’s missed an even greater opportunity.