Why do we need to study first the historical background of a certain place before digging deeper with its literature?

Generally speaking, literature is directly influenced by what is going on in society at the time. Oftentimes, literature teachers ask students to know this because it is a form of literary analysis or criticism. For example, look at The Crucible by Arthur Miller. This is a story about the Salem Witch Trials, in which Americans tried and murdered women for being witches. But it was written in 1953, almost 300 years after this happened. If you were to research the time period, you would find information on the McCarthy hearings, which was similar to a witch hunt. Senator McCarthy was overseeing the search for communists secretly hiding in the United States. The two events were extremely similar, but since Miller would have been labeled a communist and blacklisted, he wrote about a similar situation, the Salem Witch Trials.

Hope that helps!