A person should pay their credit card payment(s) on time because of interest, interest is when a loan or a sort of payment on a credit card or a sort of money object that is provided by someone else is used and needs to be payed back with the amount the person used plus a little bit of tax / interest just for borrowing the money In the first place. If you do not pay on time then your interest will go up and be worth more than the actual price of money you used on the card(s). If you make a late payment you will end up having to pay interest which probably will be more than the amount you owed previously and you will have to pay more despite it not being the original price owed.