What drives people to buy?

Working in retail gets me wondering about what drives people to buy. I am often confronted by people who are looking to purchase on a whim. They come in, see something that is cool, pick it up and hand me a plastic card. Its amazing how much I feel contempt for people like that. They may have the money or means to make the purchase, but not the meaning. I have no desire or right to actually know if they can afford what they are buying, but it gets me questioning whether collectively we have lost our ability to see the real value in products.