The answer is: to suggest the hopelessness of Zeitoun’s situation.
In the excerpt from "Zeitoun," the author Dave Eggers makes reference to Zeitoun's feeling of devastation as the sees New Orleans underwater after hurricane Katrina. For instance, the narrator describes how the whole city is submerged and that nothing other than water can be seen around Zeitoun's tent. The protagonist also looks for people, animals or machines moving, but he sees nothing until the helicopter flies around.