From their interaction with Mr. Raymond, Scout and Jem also gain a deeper understanding of the hierarchical nature of society in Maycomb. It says a lot about the town and its prevailing social values that a white man has to pretend to be an alcoholic in order to associate with African Americans. Crucially, however, Mr. Raymond comes from an old, respectable family, the kind of family of which Aunt Alexandra would most certainly approve.
Essentially, Raymond gets a pass for what the locals consider to be eccentric behavior. If he'd been born into a lower-class family, like the Ewells or the Cunninghams, then no one would try to explain away his eccentricities by putting them down to alcoholism. On the contrary, they'd say his behavior was just what they'd expect from a lower-class white, or "white trash" as they're referred to in the story.