The setting of the short story is first a commune outside of Paso Robles and then miles of thoroughfare. In fact, most of the story occurs on the road, after Pete picks Donald up from the service station.
The setting is important because it symbolizes the divergent life choices made by both brothers. Pete eventually gets out of the car, and Donald drives on. However, the text strongly implies that Donald does return to retrieve Pete.
The setting also highlights the meaning of brotherhood. The biblical undertones are clear: is Pete his brother's keeper, just like Cain was supposed to be Abel's?
It's obvious from the story that Pete and Donald are opposites in temperament, habits, and moral outlook. While Pete is an accomplished businessman, Donald is content to live idealistically, sometimes to his own detriment. As the two drive along the highway, we are led to question whether Pete and Donald can ever merge their differing life philosophies.
So, the setting is important because it highlights the road as a metaphor for life's journey. It also reinforces the divergence of Pete and Donald's life choices. At the end of the story, we question whether their divergent paths can ever unite and whether both can ever reconcile their antithetical worldviews.