After reading Why do you not review? and stumbling across Do we need a event to clear out the Close Queue?. It occurred to me that the problem might be a lack of incentive.
After 1000 such reviews, It would seem that anyone who is concerned with their rep or badges might lack motivation to continue, stop reviewing and just go back to answering questions. There's nothing wrong with that IMHO, but there may be a flaw in the policy that provides 0 rep for reviewing the close queue and badges that can only be earned once topping out at 1000.