Even without cash back, the interest earnings could be something, a 1000$ deferred payment made through credit card may give 4$ to 5$ interest payment(assuming

Even without cash back, the interest earnings could be something, a 1000$ deferred payment made through credit card may give 4$ to 5$ interest payment(assuming an interest savings interest rate of 5%, some countries have much higher interest rates), while that cash is sitting in the savings account, waiting for the credit card billing cycle to complete.