<prompt> Human: I have two credits cards. I pay off the entire balance of both every month. My dad has advised me to occasionally leave some balance on the cards, because he said if I always completely pay off the cards, the credit card companies wont be making money off of me and could cancel my cards for that reason. Is there any truth to this?Thank you in advance!Edit: Wow, I received many helpful replies very quickly! Ill continue to pay my cards off in full each month and wont worry about my cards getting cancelled. This is my first time posting to rpersonalfinance, and you seem like a wonderful and helpful bunch! Many thanks!  <response>: Nope, thats complete horseshit. Im amazed that people out there actually pay interest on credit cards just because they believe that.For banks, its like any other investment. Some customers are high risk, high reward. Theyre running up thousands of dollars in credit card debt and paying 20 interest. But theres a risk that the customer will default and they wont get their money back. Then theres those of us who pay off our balance every month. Were low reward, but were also low risk. Theyre only making 2-3 from us in the form of transaction fees, but its guaranteed money for them with virtually no risk that well default. 