The answer is probably neither---both. These programs are figured into the overall costs of carrying the vehicle--credit card and so forth. If the company is giving you rewards then it is calulated into their overall cost structure and then the fees charged to you. The same goes for any other incentive program a credit company offers. Remember they are in business and must make money.
If you pay off your balances every month and have an annual $0 fee credit card, you will incur no charges. The credit card company makes their money by discounting what they pay the vendor who let you use the card. In a situation such as this, rewards or cash back are really money in your pockets. However, if you do not use the rewards program, miles etc., then you are not receiving any real benefit. With a cash back program you are getting money back.