The first three or four answers in this interview present some interesting points about writing with a message - or, in this case, why some writers don't:
Food for thought, mostly. Whether we intend or not, I think it's hard to deny we speak from the strength of our inner voices.
I heard it said recently (to paraphrase) that it may be better if writers don't recognize their own patterns: it makes them self-conscious, makes them change course, and may even do damage to the end result. Or ... less drastically ... it may just make writing annoying. ;-)