One way to reduce the volume of low-quality questions would he to allow the OP to remove a question (perhaps only if it had gotten no responses). I have a question posted right now, collecting "close" votes, that I would like to delete. Maybe this one is another. :-) If there is a way for me to delete the question, it is not obvious enough for my brains.
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Users are already allowed to deleted their own questions without an answer with a score higher than 0 (which includes also a question without any answer). In such case, the OP is allowed to delete her/his own question, even without closing it first.
Keep in mind that deleted questions are considered a bad sign, and you could be blocked from asking any further question, if you have too many deleted questions. (Note that this is just one of several factors taken into consideration.)
Deleted questions are not a sign of less low-quality questions; it is rather the opposite. If some of your questions are deleted, it means they were low-quality questions, or they would not have been deleted. If they are not low-quality questions, they are surely questions not appropriate for the site where you asked them, which means they could be too localised, not real questions, or not constructive.