The people live in a world that tells them where to look and what to do, and not to question unusual things, like The Lost Thing, is what I think.
All is valid but it goes further than that, they not only preach not to question things that aren't ordinary (another way of thinking it is to say they don't want the people to affiliate with anything that they cannot control) but they attempt to suppress any kind of difference, from the scene where the boy is in his house, his mother/father is reading a newspaper with a caption "FLAMINGO RECAPTURED" as they attempt to round up and hide away anything with color and life, and how the tv suddenly changes to an add about getting rid of a lost thing shows that they are watching and controlling the environment around him so that he will dispose of it and think that it was a burden.
