Some banks will give you cash back for using a debit card, most likely because they profit more when you choose debit instead of credit at the register. As of this writing, Randolph Brooks Federal Credit Union, or RBFCU, gives you ten cents per purchase when you choose debit at the register for legitimate transactions. They do have rules and guidelines to keep this system from being abused.
Plus, a debit card means you are using your actual money and not borrowing money and increasing your debt level. Good for you!