They don't have much value to Stack Overflow, obviously, otherwise they would have remained opened and been voted up on Stack Overflow.
[1] http://stackoverflow.com/questions/4674609/looking-for-a-ric... (not my find, posted in another comment on this thread)
Having strict moderation standards is SO's business. I may or may not agree, but it seems to work for them.
Leaving closed questions, particularly those without answers, on their site sucking up google juice and deceptively appearing in my search results is scummy. If they don't want it on their site, they should ask google not to crawl it. And that goes squared when the question doesn't have an answer.