Why did the author choose to show only one day in the life of a prisoner?

This is a snapshot of what a day in the Gulag is like. Denisovich, like the other prisoners, exist on 200 calories a day. They try to keep warm and basically just alive. We watch our protagonist carefully avoid certain guards, scrape and trade for food and witness countless atrocities. A typical day gives us a feel for what the reality of a Stalinist Gulag might be like much as a diary or journal account.