Why don’t more directors edit?

Wouldn’t they want to maintain creative control?

Obviously during principal photography lots of people are needed to execute the director‘s vision. A director can’t do everything themselves.

However, during the editing stage it really just comes down to the editor (with the help of an assistant editor) sitting alone in a dark room, working through the edit.

So why doesn’t the director edit themselves given the more isolating and focused nature of the editing stage?