It's become routine for customers to swipe their credit or debit cards at consoles in fast-food joints, gas stations and grocery stores. So why do we still hand over the plastic at sit-down restaurants?

Pay-at-the-table systems are popular in Europe and other parts of the world, but they haven't yet caught on in the U.S., largely because equipment makers haven't been able to point to a reason why restaurateurs should invest in the gear.