1) if you live in the US you NEED a credit history and the better your credit score the lower an interest rate you will get when you need a mortgage to buy a house. If you have a few (not a ton and more than one or two) credit cards with a very low or no balance your score will be higher than if you had only one credit card or none.

2) many credit cards offer great rewards and you'll get something extra for paying your bills. Plus, you have a better manageable cash flow than if everything came out of a debit account and you don't keep track of it and you might have an overdraft.

3) security for the reasons Richie mentioned.

4) convenience.

5) you can't rent a car or book a hotel in the US without a credit card.

There is nothing bad about managing your money wisely. Credit cards can be a great tool. Irreponsible people will manage to get into financial trouble with or without credit cards ... education is the best way to gain financial control and in the end freedom.