This is all good in an academic sense, but let us not forget that literature can, and should, be read sometimes just for fun. The escape it provides from a hectic life is sometimes incomparable. Like visiting friends, one day you might just think, "I'm in the mood to read that book again."
There are several ways that learning literature is vitally important. The first, which applies to anyone, even those who don't wish to pursue a career around literature, is that studying literature develops a great capacity for analysis, for seeing the deeper picture and for seeing "between the lines" of things. This analytical skill carries over to everyday affairs and problems as well. Another reason is that it opens the door to understanding earlier periods in time. For instance, if the attitudes held by even the fierce warriors of Homer's Iliad could be taken to heart, we might all be able to speak to each other and treat each other with the "greatest of kindness." The study of literature also helps to put our own present time in perspective; to see from where we came and down what path we journeyed to get to where we are culturally today--the great hope is that in so learning we might make some greater decisions than have gone before and that we might make otherwise.
Reading literature well, and reading in general, require you to make connections and to engage in a critical process in order to discern the meaning of what is read. This is critically important in an educational sense, but it is equally important in the routine experiences of life: instruction manuals, insurance statements, contracts, etc. Learning to read literature carefully has the carry-over effect to all types of reading.
I think that it is particularly important as long as your definition of literature is not too restrictive and allows for the reading of a very wide variety and type of texts. If this is the case, the study of and understanding of literature can lead to great insight into human nature as pohnpei pointed out as well as an understanding of history through the literature of the times.
Most people would say that reading literature teaches you about the human condition. Reading great works allows you to think about what some of the best minds of history have thought about things that are basic to human existence, things like love and duty and honor and death. By reading literature, you are encouraged to think about these things and gain more insight into what it means to be human.
Literature is part of our everday life and just like history it can change.However, very known pieces will always be literature because of the language.Also, literature is is seen as a society. The important part is for you to connect to yourself and then everything, comes into place.