***Make questions unclosable until one hour after they've been asked, with an exception for flagged questions.*
What reason can you give for a non-abusive but otherwise bad question being closed as soon as possible? Bonus points for explaining the rationale behind your answer.
Since closed questions can still show up on various lists, the implication is that deletion is the goal of closing a question. Since a question can't be deleted for two days (See Shog9's comment in this answer), why the fuss about delaying the closing of a question for a relatively small number of minutes?
The notion that the signal-to-noise ratio on the home page outweighs all other considerations assumes that most people answer questions mainly from there. I almost never use the home page, preferring the newest or active tabs, or using a tag. Seeing as the number of closed questions is so low, I'd hesitate to call them "pollution." I would guess that less then 10% of any of the regular lists consists of closed questions.
Also, it seems that it is much easier to close a question than to reopen one.
If you disagree, I invite you to put your reasons in an answer or a comment before doing so with a downvote.