When people post their homework and ask for help, a lot of other users get upset and ask questions like show what you did etc. I personally have never downvoted any questions, and if I know how to solve and I got time I will write answer without demanding anything from the author. If you don't want to solve other people's homework it is absolutely fine you can just skip that question. Does it irritate you so much that you will write unpleasant comments and downvote?
I personally have never downvoted any questions....
Then you are not fully participating in the site. You should vote early and vote often.
Also, the mouseover text on the downvote button states:
This question does not show any research effort; it is unclear or not useful.
Now, as to homework questions:
There is a major difference in attitude amongst the many homework questions that get posted.
Some people post with the attitude:
I have this interesting question that I am attempting to work through, but I've run into this aspect that I'm not sure how to solve, or that I am really wondering about. How can I _____? I've attempted ______ but it seems that _____, which was surprising. Is there a different approach which would _____?
Others post with the apparent attitude:
Someone solve this stupid math problem for me so that I don't have to. I hate math and think you'd have to be either nuts or a total geek to care about any of this stuff, and also I'd rather watch TV than read my geometry textbook. I don't even want to take the time to type properly, so here is a badly transcribed copy of the problem. Solve it. Oh, I see you gave me a hint but what is the actual answer?
Of course most users aren't nearly that bad. But there is at least a shadow of that attitude coming across, or some portions of it, in most cases where homework questions get severely downvoted.
If you only want to do people's homework for them and are not interested in learning or teaching people mathematics so that they increase their understanding, you
may be are on the wrong site.
I personally have never downvoted any questions, ...
I took a look at your summary of voting (on your Activity page for the main site). It shows you have voted four times, two up votes and two down votes, and that you voted on Questions three times and on Answers once.
Do you see a mathematical inconsistency with your claim?
You've been on the site for all of two months, so your voting pattern is probably still evolving. That's fine, voting is your privilege. But I expect that in a year, you will have refined your philosophy of voting.
There are several good answers here that I won't try to repeat with mine. I generally echo the points in other answers about the site becoming associated with cheating, respect for both questioner and those looking to provide answers, and the importance of those posting questions to provide some evidence of having tried on their own before asking here.
I'm writing to add one point that I don't think is yet represented. The whole stack exchange concept is to not only provide an answer to the question in front of us but also to provide Q&A that have long-term archival value for people coming along later. HW questions that just copy-paste out of a textbook do not provide that and should be downvoted for that reason - in addition to other valid reasons provided in the other answers. Questions that provide some context about what the questioner tried and why they are stuck have a better chance of resonating with a later reader who is stuck for the same reasons - even if not on exactly the same HW problem - and correspondingly get answers that address those underlying issues.
Downvoting is one way that the community helps the system clean-up the archive over time so that the Q&A remains high quality and more generally useful.
There are two behaviors here you are addressing. One I disagree with you and one I agree with you.
people downvoting questions with little effort (see @Wildcard's second example). On this I disagree with you for the reasons Wildcard has listed.
people posting unpleasant comments - This is not acceptable and I feel as a community we need to work on this as sometimes when people downvote a question they also leave a less than constructive comment.
So yes people shouldn't get mad and leave unhelpful comments but also they should not ignore the problem and they should downvote it in line with the philosophy of this site. This doesn't prevent you or anyone from giving an answer to a poorly written homework question but it may not last or be possible if the question is closed or deleted. Depending on the question I do one or both or neither of leave a constructive comment or leave a helpful answer. I will still downvote it if its of a low standard.
There is absolutely no problem with homework questions of any level being posted on here. As a matter of fact, I have explicitly encouraged my students to post on here.
However, what I DO have a problem with, and so do a lot of people, is dumping homework style problems with no accompanying work. These I downvote and close vote. The important thing is the "style" and the "no accompanying work".
Well I personally flag or downvote questions of homework which I find content poor, not formatted where it's been told to the user to extend his question in order to know what he has tried.
Therefore I guess that rest of downvotes are for the same cause. I do not care if the question is basic, if it's good asked and they show what they have tried then I usually help and upvote to encourage those users.