from This article by J. Hess:
"As early as the latter 1800s, according to Rodney Clapp, national leaders recognized that production-oriented capitalism was too successful—ordinary citizens simply didn’t need all the products being produced. In order to sustain a strong economy, each person should become a ready spender, one who frequently bought unneeded things. Thus a shift from production- to consumer-oriented capitalism began. Following World War II, greatly expanded production capacity and a larger work force—since many women chose not to exit the work force after the war—combined to require more consumption than ever before. The rise of modern marketing and its catalyst, the television, which became readily available to the public about 1948, attempted to work North Americans into a permanent buying frenzy."

A permanent buying frenzy, huh? But how true. No, Americans haven't always been this way. But this is what drives the all-important economy.