I don't think giving close voters this reason is a good idea.
People are lazy.
They already use reasons that don't make much sense (IMO) when it's not immediately clear which reason should be used.
If we give them a "catch all" reason, most would probably use that instead of bothering providing their own explanation of what's wrong, and this might also draw close votes that would've been better suited to some of the other reasons as well.
We don't really want questions to be closeable with a generic reason that doesn't really explain what's wrong, because that would be a terrible experience for anyone who asked their question in good faith.
This option was given to lower rep users because they had no (appropriate) way to flag such questions before. I wouldn't be able to tell you the exact reason for not giving them a similar free-text option, but I can speculate that it might be because:
- This would circumvent being unable to comment (for some, at least, or there'd need to be another check to cater for this).
- They may be more likely to use the wrong reason, which might become a bigger problem if there's also a reason they can use for every flag.
- They may enter gibberish.
- They may close-flag things that should've just been downvoted or mod-flagged instead.
- They don't really need one. Flagging is only to get the question into review, where reviewers should easily be able to see (and explain) what's wrong.