"A charge card is a plastic card that provides an alternative payment to cash when making purchases in which the issuer and the cardholder enter into an agreement that the debt incurred on the charge account will be paid in full and by due date (usually every thirty days) or be subject to severe late fees and restrictions on card use"

So, you tend to optimize for different things (features, rebates, discounts vs. Interest rates and payback optiins (generally))