OK, people answer questions because,
So when a question is asked, if that question becomes a Hot Network Question their answer will obviously pull more votes and a highly up-voted question will become one of those with the caveat (That the answer are also highly up voted).
So why do so many people who answer questions not up the questions that they answer to?
For me at least, upvoting a question means I find the question useful, well-written, and at least moderately well researched. Answering a question means I looked at it and went "I can contribute here". This dichotomy means that I'll often answer questions but when it comes to voting on them they get no love; being clear enough to be answerable doesn't necessarily make a question good enough to get my vote.
We (as regular users) have no way of knowing if this is the case.
Simply put, the person who answered the question may have up-voted it. Other users who have not answered the question may have down-voted it.
A User's voting preference is not public information and is used at their discretion. This a basic premise of how the Stack Exchange Network operates. If you feel like you are being targeted by a specific user, there are mechanisms to detect voting fraud and reverse it.
There's no quid pro quo agreement in voting, I guess. The tooltip advises you to upvote a question if you find it useful.
Initially when I signed up for the site, this issue annoyed me. The question which I posted would receive an answer first, and then start receiving votes. I used to think, that if a question is "useful" enough for someone to take time and answer, then it is also "useful" enough to receive an upvote from the same person.
But later, I just decided that we can't control the votes on our posts.
There's also a post in main meta that asks why people upvote answers more often than questions, which could be useful to you.
Just for the record, there is a golden badge to be earned having a highly-upvoted (+20) answer on a -5 question.
In my mind, this is encouragement to still try and give helpful, meaningful answers to questions that are sub-par. These scenarios then act like advertisements:
Don't ask questions like this
But do answer questions like that
Whether or not an answer is available or warranted doesn't change the quality of the question.
I often will not upvote a question I'm answering simply because I feel it would be self-serving - that, as someone whose answer to the question might garner votes, raising the visibility of the question by upvoting potentially drives voters to my question. I would rather the votes on the question reflect parties with no potential ulterior motive.
I will grant you that that's defaulting to the most cynical interpretation and that I should probably reconsider - so I'm upvoting this question, as it made me think about the issue :).
