I always have cash on me too. I feel naked without a wad of cash on my person. For those who just use a credit card/ATM card everyday; I 'm not comfortable just with that. I use a credit card too but I also like the reassuring presence of cold, hard cash in my wallet.
I pay for everything with a credit card, I have the Upromise credit card and it's earned over $13,000 for my kids college. Even if it's a pack of gum it goes on the card. I pay it off every month in full so there's never interest.
On the other hand I always have a substantial amount of cash on me too, my dad always told me that if someone offers you a deal on a gun/knife , or anything else for that matter, it's easier to make the deal if the money is in your pocket. Nobody wants to wait for you to go get the money, and there is always someone else with the cash to snap it up.