You're right. I was being a bit facetious.
I think the Academy must feel that a director has to leave his or her mark on the film to be nominated. For example, in Lincoln Spielberg was involved in nearly every piece of the film making process. He is even the one who tapped Lewis to play the lead. I can't say that is the case for every film.
Also, certain directors, like say Nolan, are known for having a very distinct vision and guiding their films in ways where others may fail. I can say this is also the case for Ang Lee, where he really tries to push the envelope with the movies he directs.
I don't think that a director should necessarily be given credit for every facet of filmmaking. There are many instances where 1 specific acting performance has carried a film, and there are cases where maybe the writing was terrific, but that director was completely separate from the writing process.
It's difficult to really get inside the mind of each Academy member, but it certainly would be interesting to get a member's take on this issue.