You know, obviously you are right. But, I think people (especially intelligent HN type people) greatly underestimate how much psychological tricks affect them. I know deep down that spending with credit card is the same as spending with cash. But, I tracked my spending using cards and only withdrawing from ATMs and using cash. I spent about 20% more. And my life didn't feel any better or anything. Now I use credit cards on the big stuff- like travel, transportation costs, and other large ticket items where credit versus cash is unlikely to affect me spending habits. Point is, you get some tiny cash back, but I think for 99% of people you spend more than you get.

But only because the credit card company charges merchants an unnecessary extra 2% in fees so they can bribe you with your own money.

The cost of that lunch should be $19.60, or less.

Or 5% cashback sometimes (look at Discover More etc).

Debit cards also give cash back.