Greed is the root of all Evil

In Chaucer's Canterbury Tales, one of the the characters was the Pardoner and his story was about three men who were looking for death to kill it or him because it had taken their friend. They come across the old man who tells them that death is under a tree and once they arrive there they find gold coins. These men had been drinking and the sight of these gold coins just sparks more thirst to keep drinking. The Pardoner mentioned radix malorum est cupiditas or greed is the root of all evil and we see this illustrated as the men end up killing one another and in fact finding death itself. This is very interesting because many times we question how people can be so cruel. And this one way to see how people can be so malicious. My question is; how can people let themselves be driven or consumed by greed? I believe that in some instance in our lives we come across a person or experience something that truly breaks our hearts and bares it down to its purest form. We are all humans who once in a while will need help and a lending hand. Christmas is coming up and I remember reading the story of The Christmas Carol where Ebenezer Scrooge is the main character and he is a cold hearted old man. He has lots of money and doesn't give any to charity or to help a person in need. It takes a life experience with visitations from three Christmas spirits and a preview of his death to make him change. Now I come to my point why is it that the death of a person is what changes them? The three men at the tree could not change because death itself took their chance but for others its what they need in order to change. Why can't people just change because they yearn to do good from the beginning? Why does it take death to change a bad person? Doesn't good exist in all of us naturally?