Themes of "Why I live at the P.O" by Eudora Welty?

It's mainly an impassioned protest against the favorable treatment given to bulk mailers at the expense of individual postal customers who now have to pay 45 cents just to mail a birthday card. The narrator of the story is kind of a one-woman "Occupy movement" who has camped out at the Post Office to object to this unfair postage-rate scheme.

One can tolerate one’s family just so long and then has to decide what is best. We can pick out friends but not our family members as the old saying goes. Some have enough strength of character to accept the family members for what they are and live a better life apart.