Why does dickens include the strange section about ali baba and Robinson Crusoe?

Dickens includes the section about Ali Baba and Robinson Crusoe in "Great Expectations" to contrast Pip's literary expectations with the reality of his own life. This serves to highlight Pip's struggle with his identity and social expectations. By juxtaposing Pip's imagination with the harshness of his situation, Dickens underscores the themes of ambition, social class, and personal growth.