To me, personally, it is an issue of expertise.
I am, as far as I'm concerned, qualified to correctly answer (or at least attempt to correctly answer) many of the questions posed on this site. I feel that I am also qualified enough to judge whether or not someone else's answers are accurate.
However, I am hardly a Stack Exchange expert.
Nine times out of ten, when I see a question get closed for reasons other than redundancy, I have no idea why that question is being closed. Usually a reason is provided, but I often find that reason lacking, or I fail to see how the reason applies to the current situation. Unfortunately, I cannot think of any recent examples off the top of my hand, but regardless, I feel there is a major disconnect between what I would consider an appropriate and perfectly valid question to ask and what the general English Language & Usage community would consider appropriate to ask.
I assume that many of the lower-reputation members probably feel similarly. But maybe it's just me.
I understand that the question should show evidence of research, and I understand that the question should be understandable and clear, and I understand that the question shouldn't be "Do my homework", but aside from that, I've seen very little uniformity in what constitutes an "inadequate" question.
That's not to say there isn't a set of rules and guidelines - rather, I just haven't figured it out yet, and so I don't feel qualified to rate most questions as "good" or "bad".