It's entirely understandable that a question poster might wonder why people who have upvoting privileges at English Language & Usage and who bothered to compose full-fledged answers to the question didn't consider the question itself worthy of upvoting. In recent years, I've tried to limit myself to answering questions posted on the main EL&U site that I find interesting and worth researching. Using that baseline for answering, I almost always upvote the questions I answer.
But this leads to a split in my approach to questions. When I don't think a question is particularly interesting, but I have an idea of how to answer it briefly and without research effort and I don't want the question poster to go away empty handed, I post the answer as a comment. (Note that doing this is widely condemned at EL&U as an abuse of the comments box; nevertheless, I persist in doing it because I fundamentally disagree with the argument that answering a simple question in the form of a comment damages the site.)
Other site participants, of course, take different approaches to the questions they answer/comment on. The four people with upvoting privileges who answered your question may or may not have upvoted it: the question has now attracted four upvotes and two downvotes, and there's no telling where any of those votes came from. But it would be perfectly reasonable for people to answer a question they don't consider good enough to reward with an upvote. And indeed, the official position of the site is that such answers should take the form of answer box answers, not comments box answers.
Your suggestion that a chronically grudging attitude toward upvoting at EL&U discourages people from asking good questions here may be true, but in my view it pales in comparison to the negative effect of closing legitimate questions on knee-jerk technicalities. My sense is that most people who ask questions here do so because they want their questions answered by people who know what they're talking about. The whole reputation/reward angle is a sideshow that matters little to most question posters, I suspect.
As for why site participants are less inclined to upvote questions here than on other Stack Exchange sites—assuming that they are—I have no idea. One of the lowest-scoring questions I ever posted on this site (a question that I also answered shortly after posting) has been viewed more than 800 times, and both it and the answer have received only one upvote each. And yet that answer is also the only thing I've ever posted here that got cited in a news article in the New York Times.
If you have a question that you think is good, and you are genuinely interested in having it answered by (one hopes) well-informed people, you should feel justified in asking it at EL&U. If it gets closed, it may be that (1) your idea of a good question is a bad match for this particular site, or (2) your question, although promising, has a serious flaw that you need to fix, or (3) some trigger-happy close voters have inappropriately closed it. In the first case, you're probably asking on the wrong site. In the second case, you need to clarify something that is missing or unclear in the question as originally posted. In the third case, the site truly is shooting itself in the foot by rejecting a valid and potentially valuable contribution for no good reason. But in all of these cases, the prospect of being rewarded by EL&U's upvoting system is objectively unimportant. I hope that you won't let it determine your interest in and future contributions to this site.