This is an interesting point, and I have seen this happen quite a few times.
The first guy tries to moderate the question, edit it for improved formatting, re-tagging and search for appropriate ways to help the OP use SO to ask better questions, while the second guy rushes in to get the points.
But what happens if you find a duplicate and just copy-paste (with small adjustments) the best answer? Should that get upvoted?
You are not obligated to search for duplicates, but you are probably expected to, in cases of questions that are too obvious. While it seems perfectly caring and helpful to answer the OP's personalized question, I am generally against posting "Try this" kind of answers, which is the usual answer to questions that are obviously over-explained online.
IMHO, I see SO as a source of understanding programming rather than chat with an expert and get your question solved kind of site.
So, if the question is already answered, even if it's not an exact duplicate, shouldn't we all feel obligated to help the OP learn how to search for answers, instead of pasting it for them?
P.S.: Sorry for the late answer.