In the end, I don't think that it's something writers should worry about. You can have a masterpiece which really pushes societal expectations, or you can have one which does nothing to comment on politics. Though, having said that, when we look to the past we find that it is the progressive pieces, the one which challenged their societies, which are the ones which have remained popular. But I'm not sure whether this is because the author is being very progressive, or because the novel is doing something new ("A woman doing X? What an interesting story idea!" for example). Perhaps a progressive attitude is more likely to produce original artworks? I'm not sure. But, either way, I don't think writing needs to have something to say about our world in order to be of value.
(Don't miss today's Finger Puppet Show!)