There are alot of reasons why someone wouldn't want to pay it back immediately, even if they could. It's not a mistake that the most well off people are often the most in debt (low interest, like mortgages). I don't make the rules, but it doesn't mean I shouldn't take advantage of how the game is played. While interest rates are so low, it is very easy to make more money on that money than the interest rate it cost or borrow it.