The quotations are helpful because they provide about of context for the illustration. Otherwise, the reader wouldn't know what was going on in the picture. It is easy
to distinguish between quotes and quotes from Kafka because the text is either a quote directly from Metamorphosis, or it is a quote describing Kafka's work in Metamorphosis. Since it is highly unlikely that Kafka is talking in third person, the reader is easily able to understand that it is not a quote directly from Kafka.
Mariowitz hoped to expand beyond his scholarly audience and reach an audience that typically wouldn't read a book like Metamorphosis. Since they are not adapt to this higher level reading, they would need more help following along this sometimes confusing story. In order to appeal to this new audience, he decided to tell Metamorphosis in a way that would appeal and interest the average reader. This should add to his reputation in the academic world because he is adding to its members. People that typically wouldn't read Kafka or writers like him might become interested in them after reading Mairowitz collaboration with Crumb. Instead of keeping the Kafka's writings a secret to members that are a part of the academic world, Mairowitz decided to help educate everyone, instead of that select few, which is applaudable.