But that only applies to people that have debt, no? Those who want to spend money that they currently do not have?
Essentially, yes. . America is a nation of debt. It's considered 100% normal to have debt in the USA, and it's unusual for someone to have none. This is why Americans all have big houses and cars and whatnot. The high price of university education, which is normally paid using loans, probably has a lot to do with this. When you start out your adult life with 10 years worth of loans to pay off, it's no big deal to get a credit card and just continue buying things you can't afford. What's the harm at that point... (I tried to explain what a credit card is to some of my Czech students and I couldn't get them to understand. They know about debit cards, but this "instant loan" concept was new to them.)
Your credit rating is essentially a nationwide reputation rating system for how likely you are to pay off your debts. So when you decide to buy something you can't afford (usually a car or house, but Americans tend to buy other things they can't afford as well), you can get a loan for it. If you have low or no credit, it's hard to get a loan, or if you get one, the interest rate is really high.
acetech09: you can't get credit without debt. Credit cards just create instant small loans every time you use them. Paying off your debt right away is a good thing, but if you don't have debt in the first place, you can't pay it off, so you can't get credit. You have to owe someone money, then pay it in a timely fashion, in order to build credit. Whether the debt is short-term or long-term isn't really a big factor.
BFEL, as others have said, you don't need a credit card to build credit. Just get a phone plan and pay your bill every month and you'll be fine. Whatever you do, NEVER EVER EVER buy something you can't afford to pay for right away, unless in case of a real emergency. Just because most Americans have debt, doesn't mean you have to have it as well. If you decide to get a credit card for emergencies, make sure you get one with no mimimums on it, and really save it for emergencies only. Future you will thank you.