In Colossians 3:5, Paul equates covetousness with idolatry:
Put to death therefore what is earthly in you: sexual immorality, impurity, passion, evil desire, and covetousness, which is idolatry. (Colossians 3:5)
Well, in Genesis 1:29, man is given explicit permission to eat any plant.
In Genesis 2:16-17, God forbids consuming one fruit (incidentally, the eating of animals is not prohibited, not is their use for sacrifices).
So in the whole field of potential possessions, man is limited. Why? Because to limit man’s desires implies that they are not meant to receive total fulfillment in created things (Ecclesiastes 2:9-10). Man’s desires are functionally infinite (Ecclesiastes 3:11). The created order is simply not suited to the vastness of human desire.
Covetousness is the notion that created things are the primary point of human desire. It arises from the attempt, whether implicit or not, to fill the infinite void in the human soul with the limited field of creation.
And so coveting, by replacing God with created things, is idolatry in a way that other sins besides actual idol worship are not.