They spend more than they can afford when they are offered credit, and then spend years paying off the balances they've racked up. Credit got to be convenient, even comforting. I can buy something and not worry about paying for it until later, and I don't need to write it down in my check register. With cards, I get monthly statements that tell me exactly where my money went. I don't have to wonder, like I did when I mainly used cash.
Credit cards offer protection.
With cash, if it's lost or stolen, kiss it goodbye. It may seem like a piddly sum, but I do it for the added convenience of not having to write all those checks. One day, I woke up and realized that since all my cards had zero balances and I didn't need to worry about rates, I might as well take advantage of the cards offering rebates and rewards. Most frequent flier cards charge annual fees, making them too expensive for someone like me who doesn't charge enough to make them worthwhile. Neither costs a thing if you make all the payments on time and pay off your balance each month.