To my mind, the only reasons to close questions at all are to:
Express the official policy on what questions are acceptable, in other words, quality control. We don't want to accumulate lots of questions like "What is your favorite thing about math?".
Take the question off the Unanswered list when we know there's no chance of it ever getting an answer.
I think the "unclear what you're asking" close reason is certainly needed, but it's something that should be used when the OP hasn't returned to reply to comments in maybe a day or so. Once it becomes clear that the OP isn't coming back, and the question is too vague to be answerable, then we're clearly in situation (2).
Several times I've seen questions closed very quickly - I would say anything less than 24 hours is quite quick - with the "unclear" close reason. I don't believe this serves either of the above two purposes. The reason is because we need to give the OP a chance to come back and reply to comments requesting clarification, or edit the question. Just now I saw an elementary question which was just a little ambiguous, probably because the OP simply mistyped, attract a close vote inside of fifteen minutes. Give the guy a chance!
It's simply less efficient to force a novice user to edit their question, come to the meta, post a request for reopening, and then wait around for it to happen; than it is to just talk to them using the comments feature that StackExchange provides for just that purpose, and work it out in often a few hours. Meanwhile, I assume that closed questions no longer show up on the front page, so fewer people will be available to come across the question and help the OP clarify it. Besides just the time issue, a new user probably won't even know where to appeal for reopening or even that it's possible, not to mention that on a psychological level they may just take the closing as a pretty clear "we don't want your kind around here" sign and just not come back. At least once in the past I've answered perfectly fine questions after requesting reopening myself, only for the asker to never return.