All high school and most college students are required to study literature because first and foremost it develops reading skills and by extension writing skills. These are, at their most basic, two compelling reasons to have literature studies as part of a well-rounded curriculum.
Beyond these two reasons, studying literature develops critical analysis skills as well. Reading a well-written novel, short story, poem, or play engages the reader in the lives of the protagonist, antagonist, and supporting characters in the work. The reader sees the world through the eyes of different characters; he or she can ponder whether the viewpoints and beliefs of these characters are like their own or not.
Furthermore, the study of literature allows a reader to experience 'truth' in a fictional setting without the constraint of 'facts' to tie them down. Certainly non-fiction works are useful and insightful reads. However, the freedom afforded by fiction to create a story based on imagination, takes the reader to a different place, where they see the world from the unique perspective of the writer who is embracing artistic license to tell their story.