Dependency: Of course the people who can't afford to keep their CC balance at zero end up paying for my peace of mind via increased interest rates. Ultimately CC's are an unfair burden on the "working poor" and become "just another bill" when they inevitably hit their limit (been there, done that). The sad fact is that if everyone at every point in their life could afford to keep the balance at zero nobody would pay interest and CCs would not exist.
That last sentence is false and shows you don't fully understand what you're discussing. The merchant is charged a fee, usually a small percentage of the transaction, each time you use your credit card. Even if you never personally pay interest because you pay in full each month, the bank issuing the credit card is making money from your use of that card.
Incidentally, this is also why some small, local, mom-and-pop stores won't accept a credit card unless your total purchase exceeds a certain amount. The fee they must pay isn't worthwhile to them if the transaction is too small. Larger stores are better able to absorb it and just consider it a cost of doing business.