Why should we bother having employees sign their time cards?

Q: “Is there merit to having employees sign their time cards? Is it important to have a certification that the hours shown represent an accurate accounting of time worked? Is there any type of liability if the employee simply uses an automated system of hand or card swipes and never 'approves' their time, either automatically in the computer timekeeping system like ADP or in writing on a printed timesheet? What might be the issue if this does not happen?” – Kary, Maryland