Why do I need to learn context when studying English literature?

Literature is hugely influenced by the contexts in which it is written. If someone said a single statement, such as 'I'm so surprised I got a C in my test' you wouldn't be able to understand what they mean, so here if they're happy or sad, without context. Social, political, economic, historical and biographical details all add to the fabric of a text and without them the full meaning can be missed. You might not agree but every single thing you read you already know some of the contexts - even if this is only the date it was written. Take for example War poets such as Rupert Brooke and Siegfried Sassoon - their poetry is so effective because it reflects the horrors of the Great War, and if we didn't know their personal experiences in war their work would be less poignant and powerful. Similarly, through looking at context critics now think that Shakespeare was using his plays as a code to give political commentary on events in his time. All these details are essential in understanding literature fully.