This is a good and important question. English literature is important in many different ways. Let me list a few of them.
First, English literature tells us about the history of the English speaking world. In other words, through this literature, you are able to learn about ourselves and our history.
Second, English literature also teaches us many lessons that have universal themes, such as love, war, desire, justice and many more. When we read these topics, we become much more sophisticated in our thinking and our view of the world expands. This makes us better citizens.
Third, English literature also makes us think, as we might not necessarily agree. We will have to form opinions and convictions of our own and the reading of English literature can aid us in the process.