Shoes, socks, and coats are all necessary to keep a person warm, and Jews were often on the run and in cold places.
The young narrator, Stopthief, always remembers being on the run. It is important to him to have a proper coat and shoes because there is always snow in the winter, and they sometimes have to sleep on it.
We went from that place to another, and another. We slept in many places. All were cold. (ch 9, p. 40)
Boots and socks are also important for running. Stopthief and Uri often have to run from the Jackboots in order to escape imprisonment because Jews have never been respected, and soon are being rounded up.
The Holocaust was a difficult time, and even the basic tools of survival were often denied to Jews. Having what you had, and hanging on to what you had, was the most important thing.