Somehow I feel that this issue has come up already, but I was unable to locate an existing discussion that covers it.

When I vote to close a question, I'm presented with a list of reasons for closing. This list seems inadequate. In particular, there isn't anything like "too elementary" or "homework" (unless you count "off topic," which I don't think is quite right).

Do others feel that the list of reasons is inadequate? Does the software allow this list to be expanded? If so, then what additional reasons should be added to the list?

Yes, it's inadequate, and no, it can't be expanded.

I actually don't think it's so bad that it's inadequate. If your vote to close is effective (i.e. if the question actually gets closed), then it will be public information that you voted to close. So there's really no reason for not leaving a comment explaining your vote to close.

Any list of reasons will ultimately be inadequate, but leaving a comment with an explanation allows you to communicate any reason you can put into words. Aside from all the benefits of clearer communication, the habit of leaving (or voting up) a comment when you vote to close forces you to actually expend some energy to make sure you have a good reason for voting to close.