If there was one thing the Curtis' never ran out of, it was milk. The white liquid that tasted like water, but was better than water, because it quenched your thirst AND gave you calcium to make strong teeth and bones!
Now, why would the Curtis' always have milk around? Surely chocolate cake was more important. Or cigarettes, or coffee, or a number of other foods, drinks, and drugs. It was something Ponyboy had always wondered, but never got a straight answer.
Because the reason was that Darry and Sodapop were trying to make Ponyboy tall. He was a little short.