In my opinion the root of envy and greed stem from a direct self loathing. Those who desire more than they need and the things of others have a deep disdain for who they truly are. The comfort in your own skin is tattered from feelings of low self-worth. Not having a quiet place within your heart to just "be yourself" and allowing feelings of "who you are" to be good enough, drives people to desire grander more glittering possession's.
For many, this grasping of things is a conditioning built in from the moment they first cast their eye's on a TV commercial. The brainwashing and re-vamping of what self-worth is, becomes ingrained in tiny minds and only grows more greedy and gains greater envy as the marketing and ad world mold and shape how to be a person worthy of societies admiration's.
Some may even say it all began in the garden of Eden, when greed first took a bite out of mankind.