More specifically: Is there a functional purpose to closing an answered question that had a specific, right answer and is highly unlikely to elicit any further answers?
Closing a question prevents new answers, but if there is already a right answer and it's obvious that no one else is going to be answering it then from a functional standpoint this isn't really necessary for that purpose.
Of course someone may be closing a question because they want to make a statement to the author and any passer by's about the quality of the question and perhaps guide them not to ask similarly bad questions in the future. That's all good and fine, but does this do anything to the question aside from preventing the already unlikely chance of a new answer?
I'm thinking that it doesn't since closed questions still appear in searches, but I was just curious.
Edit: To be more clear, what I meant by 'functional' is whether the software handles closed questions any differently aside from disallowing more answers. The software doesn't know or care anything about how people perceive questions.