Why is greed so strong?

Greed and envy are so strong not because of their inherent intensity but because of the difficulty in resisting the public pressure to be a wolf with the wolves. Change the social climate, the values that are either approved or disapproved, and the change from selfishness to altruism will lose most of its difficulty.

Greed is a bottomless pit which exhausts the person in an endless effort to satisfy the need without ever reaching satisfaction.

Close observation shows that while the selfish person is always anxiously concerned with himself, he is never satisfied, is always restless, always driven by the fear of not getting enough, of missing something, of being deprived of something. He is filled with burning envy of anyone who might have more. If we observe still closer, especially the unconscious dynamics, we find that this type of person is basically not fond of himself, but deeply dislikes himself.

--Erich Fromm