Why is Aunt Alexandra so old fashioned in To Kill a Mockingbird?

Aunt Alexandra, Atticus's sister, quickly establishes herself as a conservative, old-fashioned presence in the book. She disapproves of the way Atticus raises his children, especially Scout, and she attempts to "improve" Atticus's parenting style by coming to live with him and his children during the second half of the novel.

In a nutshell, Aunt Alexandra is old fashioned because she is highly preoccupied (one might even say obsessed) with the Finch family lineage. Despite the fact that Atticus is not terribly wealthy, the Finch family actually has a history of distinction in the novel and is known as one of the "good" families of Maycomb (this means that they have historically been wealthy). Atticus hardly seems concerned with the class of his family, but Aunt Alexandra seems anxious to preserve the family's image and maintain a place of distinction in Maycomb's social circles. As such, Aunt Alexandra seems old fashioned because she's obsessed with the past and its outdated class system and social hierarchy.