These things often don't see enough velocity for closure, which is why they're culled iteratively. If we restricted the reach to only closed questions, a significant amount of stuff that's not likely to help anyone (or worse, blocking someone from asking a better question altogether) wouldn't get deleted.
As Shog notes in comments, they get a pretty long life to live if the community hasn't marked them as potentially harmful with votes, but tend to become things that folks trip over in search engines if they remain in that state for too long.
A strong indicator of a good, clear and useful question is it receiving at least one answer, ideally one up-voted answer. It could be that some interesting stuff gets caught in that crossfire due to just asking at an unlucky time of day and slipping through the cracks. But, presumably, if it's worth asking - it'll get asked again :)