<prompt> Human: 21 year old- not understanding credit cards. Why do people keep money on their credit card? I know several people who like to keep money on their cards that they could easily pay off but continually do this for years. Does this build credit? Am I missing something important? From what Ive gathered, using the card and having a record of paying at least the minimum builds credit, but why not just pay off the whole bill instead?  <response>: Nope, you just cracked the code buddy. Youre already more financially literate than 50 of America 