What's Wrong with Mentioning a Screenwriter?

       I've been reading film reviews for quite some time. Something I've noticed over the years is the constant refusal to mention screenwriters at all. Unless you are Charlie Kaufman or the person who also directed the film, you will not be mentioned by any critics for your work.
     For example, I've read several reviews for Darren Aronofsky's newest directing gig, Black Swan, and the screenwriter is never mentioned. Was his screenplay just this barebones treatment that Aronofsky magically turned into a film? No, it was the dialogue and actions of the characters in the film. What's the deal? How about the films of David Fincher (Pre-highly publicized Aaron Sorkin collaboration). Can you name any of the screenwriters? Probably not, because the director is always mentioned first. There's even a review of Seven that commends Fincher's decision in ending the film the way he does. As if Andrew Kevin Walker's screenplay had nothing to do with this.
     This isn't how we treat playwrights or novelists. We even treat the writers for television shows with a certain prestige that isn't given to television directors. Matthew Weiner is the star of Mad Men's crew, yet he has only directed four episodes. I'm just confused, world. Why aren't screenwriters given the credits they deserve? Of course, the director decides the tone of the film and projects the screenplay how he sees fit. It is definitely a director's medium, but this does not excuse leaving the screenwriter completely without merit. I mean, if you didn't have a screenwriter you'd just end up with Gerry...

     Thoughts? Anything to add?