The Catcher in the Rye takes place sometime in 1948 or 1949. The story itself lasts only over a long weekend. The time is important because it places the story very shortly after World War II. What that also means is the adults in the book are adults that have likely lived through the war, the Great Depression, and likely the Roaring Twenties. They have seen the world come full circle. They saw the massive prosperity of the 20s, the cataclysmic downturn of the depression, the horrors of the war, and are again enjoying the prosperity that has fallen on postwar America.
Holden's attitude throughout the story is a drastic contrast to what the rest of the nation was supposedly feeling. What Salinger is showing is that darkness and depression still do exist despite the overwhelming prosperity that is present. Holden's attitude highlights a hypocrisy that existed among the population. Holden can't stand "phonies," and that seems to be all he sees: people who are covering up their true emotions by going places or buying things. Holden sees it all as phony.