It's the classic psychological argument needs vs. wants.
You need Maslow's hierarchy: Food, shelter, safety, etc...

Yet the wants include a 3000+ sq ft home in a "master planned community" with a highly rated school, and a "nice" car at $700 a month on 72 months, 300 channels of cable TV, an I-pad, etc...

Rarely do you see a member of the middle class that says, you know what I'll just live in an upper lower class neighborhood and drive a hooptie, while being happy making 60K a year, and having 20K a year disposable income. I'll clip coupons and drink cheap wine foregoing the Silver Oak Cabernet. For most, the vast majority of their possessions are not required to function in daily life. It's like the Container Store - it's a store completely comprised of items that are not in any way required to function in everyday life!

People generally spend almost exactly what they make (or more, calling for credit). As a result, there's always additional wants and the only way to achieve those is with additional income. That's the perception at least.