I've been doing similar. I realize that some people prefer to spend their money, including grocery shopping, somewhat spontaneously and for those people credit cards are probably a bad idea. But if you plan a monthly budget ahead of time there's almost no reason not to be using a credit card with a good rewards program. Different people value different things so what rewards program is the best is a more complicated issue. But purchasing via credit is only detrimental if you're spending more than you can pay back.