Anyway, the citation is from the late David Foster Wallace, and immediately hit a chord with me:
The task of literature is to "disturb the comfortable and comfort the disturbed".
A simple as that. In many ways I agree with this sententia - it certainly covers central sectors of why literature is such a vitally important part of human society. Reading is important in order to challenge your own world view, and to expand both your horizon and vocabulary. The expanding of vocabulary also has the side-effect of clearing and adding depth and discriminative powers to your mind, something not quite unheard of. Through literature you enter completely different spheres than your own bubble of reality, and in many ways this is a means of gathering experience from fields you would never come in contact with in other arenas. You can sharpen your mind in the meeting of other minds, who through literature has found their own particular style - yet another benefit of a novel, short story, essay etc. A piece of literary art is (usually) a thought-through, carefully composed world of its own and in many ways one of the finest gifts a human can give another human being. "This is my world and you're welcome to enter it" seems a good caption to follow every book.
Quite as important as stirring up the far too comfortable sphere of consensus that most people more or less live in, is the other dimension of Wallace's words: To comfort those who find life hard and difficult and feel outside the rest of humanity. This is also a place many of us will find ourselves from time to time and it can be a great comfort as well as a reality check to read about other people's experiences and thoughts and through this find ourselves to be part of a whole even though we didn't believe it to begin with. We can even find soulmates in authors we have never met and will never meet - this, to me, is one of the greatest gifts literature can offer.
Literature is of course also an outstanding (probably the best) method for conservation of the thoughts and ideas of old masters.
I guess much of what is written in this post comes as nothing new, but it is still nice to remind ourselves sometmes why we read. And of course there are many more reasons for reading than what I have listed here. Want to add some?