It's not free if you can't pay it off that month. And CC transactions are already priced into items the retailer has. I don't get a discount if I pay with cash. I pay the same price as everyone else. The discount only works if you try to haggle with small businesses. Plus I'd rather let my cash accumulate interest in my account and pay off my bill at the end of the month, instead of spending cash on a particular day during that month.
If more people used their debit cards more often, business cost drops and it reflects in prices down the line. This idea of borrowing money for EVERYTHING, just because you can pay it off at the end of the month or whatever, is highly disturbing.
Many places offer cash discounts. If more did that then there would be no problem. You are not really borrowing money you are using a service.
I got $500 cash back last year on my American Express blue. I'm pretty sure that's more than whatever discount your retailers might have given you. I also have about 200k frequent flyer miles from years past. And because I pay off my bill at the end of each month, it has cost me nothing... or nothing more than you had to pay.
Every restaurant I go to is the same cost, cash or credit, as are grocery stores, gas stations, clothing stores, airline tickets, hotels, car rentals, etc. Any fees that are being passed along to customers are being passed along to all customers. There may be the occasional place where you get a discount for cash, but they are few and far between.
Bonus rewards. I get 5% back at gas stations, 2.5% on utilities(Including DirecTv) and supermarkets. Get 1% back on regular purhcases. Can go through online vendors and get even more. Target gets me 8% online. Check cards don't get me all that.
On my check card, I actually get rewards points, but it is something like 1 point for every 4 dollars spent. Credit cards tend to do better rewards.