Because mastercard/visa don't personally bear any risk they are very happy to process refunds and chargebacks in the customer's favor. It's not a perfect system, but it's much better than direct bank debit where the customer has very little recourse. There is also a significant privacy issue. Today my bank can only see the sum total of my credit card purchases but not what I buy and from which vendor. Amex can see what I purchase but knows very little about me otherwise. I like this separation, and I like that it's hard for the government to get a complete picture of my financial affairs. I know credit cards get a lot of hate (here and elsewhere) but as a consumer I think they're exceptionally convenient.