You're getting downmodded because you have no idea what you're talking about with credit cards. You don't have to pay a 7+% for ANY purchase at all as long as you pay your monthly statement in full. The ONLY time you end up owing ANY interest on your purchases is when you decide to (or have to) carry debt from month to month, and then the APR on that debt is generally in the 20% range - absolutely atrocious rates btw.
So yeah, I use a credit card for pretty much every single purchase I make because:
A) It's super convenient - especially for gas.
B) I get between 1% - 4% back on every purchase I make. Every year, I end up getting north of $150 back just for using a card over cash.
C) I hate carrying a wad of cash around and getting coins back.
D) I get detailed reports of all my spending at the end of each month from the card that can easily be imported into the finance program of my choice
E) I'm protected should I ever lose my wallet, I lose nothing as long as I report the cards lost fairly quickly. I'd lose whatever cash I had if I just used cash.
The only time I generally don't use a card is when I want to support local small stores - mostly restaurants. Since paying in cash generally puts 1-2% more of the purchase in their pockets.