In my opinion, the variety of characters in the Bennet family in Jane Austen's Pride and Prejudice allows the author to draw attention to the many kinds of people within the society of which she is a part, hold up within the reader's view the chasm within society based upon wealth and station, and how different characters are affected by the variety of characters that interact with the Bennet family.
One reviewer praised Austen's:
...characterization and her portrayal of domestic life.
It is also stated that these elements provided a depth to her novels, and a departure from the popular gothic novels of the time.
[She concentrated] on personality and character and the tensions between her heroines and their society...
In terms of the variety of characters, consider Wickham and Darcy who are both members of the upperclass. However, the distinction between the two men in terms of moral character and ethical behavior show them to be completely different. This becomes appallingly apparent when Wickham elopes with Lydia—with dishonorable intent. Darcy, who is such a snob at the beginning of the story, goes through a transformation because of his interaction with the Bennet family, especially Elizabeth, that is not of the upperclass. Elizabeth herself, throughout the novel, also learns to see Darcy differently, though she has little regard for him at the start of the story.
The interaction between characters allows for a study of the society of which Austen was a part. Her novel examines the...
...delicate business of providing proper husbands and wives for marriageable offspring of the middle class...
The variety of characters from the upperclass and the middle class allow the opportunity to examine the differences of people and their behavior based on social standing, that people can change, and that one should never judge anything or anyone simply based upon one's perceptions, but rather deal in facts.