My first real job after college was with an outfit that investigated insurance claims fraud. This turned out to be something of an eye-opener for a young man who had absorbed the conventional wisdom that crime was caused by poverty. There were certainly plenty of "slip-and-fall artists," drawn from marginal elements of society, who feigned injuries for cash. But that didn't explain the doctors and lawyers who were implicated in sophisticated fraud rings that staged phony auto accidents involving carloads of putative injury victims, all crying "whiplash." Why would affluent professionals who already enjoyed a favored position in society risk their reputations and careers -- not to mention serious jail time -- in a sleazy criminal enterprise? The only explanation I could come up with was that they were greedy.
Why do we always want more? One theory is that there is survival value in being greedy. In a competition for scarce resources, the creature with a strong desire for more is more likely to get it and therefore to survive and reproduce. Assuming there is some genetic component to this, the desire for more would become a favored trait in the gene pool. But what happens when scarcity is replaced by abundance? There does not always appear to be an on/off switch or thermostat that regulates the desire for more once basic needs have been satisfied; hence, the phenomenon of doctors and lawyers moonlighting as crooks.
In Buddhist cosmology, those whose lives were given over to greed are consigned to the Realm of the Hungry Ghosts. The Hungry Ghosts have distended bellies and tiny necks that make it impossible to swallow, so they can never satisfy their hunger. The Buddha in this realm holds out a bowl containing the "gifts of the gods," hoping to awaken in the ghosts a hunger for truth that will replace their craving for lesser fare. To be freed from this realm, the ghosts must be willing to look up. In this there are echoes of Dante's Purgatio, where the greedy are bound hand and foot and left lying face down on the ground. This is because in life they did not lift their eyes on high but set their sight on earthly things.
So why do we want more? Perhaps it is because we feel empty, even when we are not -- or at least not in the sense of being truly hungry or poor. Our emptiness is existential. We feel, deep down, that we are empty vessels that must be filled if we are to have any existence at all. Advertisers know this and exploit it. I consume, therefore I am. The trouble with this notion is we are not vessels and so cannot be filled. The truth is that we are nothing at all. Trying to achieve fullness is futile and also unnecessary. We mistake our essential nothingness for emptiness, but they are not the same thing. The reason we cannot be filled is that in our nothingness we are already full-up with everything that is.