Sure, the occasional customer gets into a cycle for credit card debt and ends up paying big interest. That’s not where credit card companies make their money though. There’s a fee for the merchant to process each transaction, that’s the main revenue source. Then if we’re talking about a store card, they get the ability to track your purchases everywhere you use that card, and use that info to do better marketing, merchandising, and just generally get better at selling people stuff. It’s nice to make a buck when people buy things from your store, but it’s even nicer if you can make a buck when people shop elsewhere too.