Another reason could be that they're not willing to absorb the inevitable bank and credit card fees that results from using that card. I think there's something like a 2% transaction fee for every purchase that comes right off the top. Merchants are not allowed to add that 2% on top of the purchase price per their merchant agreements with Visa and Mastercard. The best they can do is build that into the price of whatever they sell. If you're paying off a debt, they would have to eat that 2%. (Don't quote me on that rate. Debit cards have a different rate from credit cards and I have no idea what the real rate is.)