Why do the man and boy go to the man’s childhood home?

The man and the boy have no particular destination other than travelling South towards the ocean. The father's childhood home represents his identity. Like all homes it is empty of people and rotting. It is the idea of home that makes the man want to go. He wants to feel a place where his once identified with and show his son a little of a past that he remembers when it was not part of the dying world.