<prompt> Human: my dad uses AMEX to buy everything: clothes, groceries, gas, everything and anywhere and anything that accepts it.he tells me all the time that he just gets cash back all the time. he earns rewards or points or something and then applies them to his balance and his balance is less.is there a catch to this method ? he always asks me why i dont do this and gets upset when i dont have an answer. for reference, i live very comfortably with no credit cards, i only use a debit card. im only spending money that i own already.  <response>: Yes, you are missing out on 2-5 of every purchase you make in cash back if you arent using a CC. 