Chapter 13 of "To Kill A Mockingbird" goes into the history of Finch Landing and Macomb, Alabama. Scout informs the reader that "Macomb is an ancient city." She also relays that
"although Maycomb was ignored during the War Between the States, Reconstruction rule and economic ruin forced the town to grow. It grew inward. New people so rarely settled there, the same families married the same families until the members of the community looked faintly alike. There was indeed a caste system in Maycomb, but to my mind it worked this way: the older citizens, the present generation of people... were utterly predictable to each other."
Scout is letting the reader know that change doesn't happen in Maycomb easily because traditions are so strong and new ideas are so hard to find. The same people have been in charge for so long that when they die, or get to old to make the rules, their relatives and children take over. These people have the same value system and beliefs that the previous generation had because they are such an isolated community.
When Aunt Alexandra, Atticus' sister, arrives, one of the first things she does is try to teach the children "their place in society". This means that she tries to give the children as sense of pride in their ancestors and thus a sense that they should take their place beside their honored ancestors as town leaders. Ironically, all Scout has heard is about "Cousin Joshua" and how he "went round the bend". Alexandra is horrified and tries to get Atticus to help teach the children about their ancestors, but Atticus retorts that he can't remember because he's getting" more like Cousin Joshua every day. . ." If Alexandra is an example of other people in Maycomb, then that means the citizens of Maycomb are all aware of "their place in society". They are all aware of their ancestors and expected to follow in their footsteps. If that is the case, no one in the town wants to or is allowed to "step out of line" and things remain the same as they always were.