I found another post that is this same question, I copied it for you.
Steinbeck uses parallelism in the Grapes of Wrath because he wanted to emphasize the fact that the people were not happy when the new migrant moves into their neighborhood. He also shows how the migrants form close bonds with each other due to their similar struggles and life experiences. Parallelism is the balance between two or more similar words or phrases. By using parallelism, the author improves his writing style and readability of his novel. Parallel construction also improves the reader's understanding of the story.
