The $20-T debt of the US government alone will never be repaid. If the Chinese come knocking asking for the repayment of the said debt, see how the government try to become hostile and engage in a war (hopefully not) with China.
China won't do that because they very well know that it isn't going to happen, and that it will also affect themselves. Don't forget that owning debt that won't ever be paid is a weakness on its own. If you expose that weakness by asking for repayment, you are basically shooting yourself in the foot. In other words, it's not as black and white as it may seem, there is way more to it than we know.
In the end, most people strongly dislike debt, yet don't try to prevent themselves from exposing themselves to that, just because they want something right now instead of next year. It's what the system is built on. Debt has become so normal, that we have to swallow its side effects and there isn't much that you can do other than to not participate in something that's causing all these problems.
I really thought that after the credit crisis it would be a whole lot harder for people to expose themselves to debt in form of easy loans and whatnot, but it seems easier than ever before to tap into your credit limit (some times worth tens of thousands of dollars). It's insane. So much money so easily accessible is tempting for a lot of people.