While recently thinking about a scene from the Clone Wars series where Anakin (and possibly Asoka) were paying for something with a number of physical credits, it dawned on me that I have never seen anyone pay with a credit or debit card in Star Wars. So, do credit or debit cards exist in Star Wars?
Without high-speed, high-bandwidth interstellar communication to check the balance in real time, issuing credit cards would have to rely on the credit rating of the individual.
The characters we follow in Star Wars are interstellar travelers or living on relatively primitive worlds. Many also have a questionable credit history. Hence loan sharks, who follow the debtor and break kneecaps to collect the debt.