How is "The Rocking-Horse Winner" a critique of the obsession with materialism in modern times?

The mother in this story lives a very comfortable life in a fine house, but is never satisfied. No matter how much she gets, it is never enough. Through her, and the fate of her son, Lawrence critiques a world in which material possessions are more important than love and human relationships. We are told early on that the mother is unable to love her children. To win her love and approval, Paul begins to ride his rocking horse feverishly so he can learn, supernaturally, what horse will win the next race. No matter how much he wins, though, it is not enough. He kills himself trying to get more. Lawrence thus suggests that we can all potentially kill ourselves with overwork when we put materialism at the center of our lives, and illustrates that possessions alone will never fully satisfy us.