Why do Americans have an undying need to consume?

We are a consumer nation. People all want their big SUVs, their iPods [iPhones], and the biggest house on the block. Whether these goals are realistic or completely unobtainable (like those of us who can't afford to buy everything) they still linger in our minds, "I wish I had 600$ to buy this iPhone". This mindset seems to almost make people ignore the issues facing our country, unless it directly effects their ability to consume.

Why are so many Americans caught in this super-consumer mindset? And when did this start happening to America? (aka when did American's start becoming so self centered)