Explain the purpose of the father’s flashbacks. Why do they happen so frequently?

The man's recurring memories and dreams poignantly underscore, often by contrast with, the hopeless destruction and chaotic violence which characterize his situation in reality. These passages also demonstrate the man's struggle not to succumb to wishful fantasies but instead to persevere throughout the journey's seemingly insurmountable hardships. The vivid excerpts from his past life remind him (and the reader) that such a life did once exist, despite the hellish present circumstances.