Seriously, why hasn't a video game been nominated for the Hugo and Nebula Awards?

Of all the landmarks in science fiction history that we predicted would happen in your lifetime, there's one that I really can't believe hasn't happened yet. Why hasn't a video game been nominated for a Hugo or Nebula Award? With games like Dead Space, Bioshock, Mass Effect and Portal featuring complex world-building and multi-layered storytelling, it's hard to imagine why science fiction's top awards haven't honored them yet.

I asked about this on Twitter, and we also had some dicsussions about this in comments yesterday — and reasons people brought up included uncertainty over whether a video game counts as "long form" or "short form" as a dramatic presentation. (I'd guess "long form.") Also, the perception that video games have derivative, unoriginal storylines — which is probably equally true of a lot of the movies that get nominated in the "long form" category. And just the notion that people haven't caught up to the evolution of video games yet.

But why do you think video games have been passed over by the major SF awards? (And don't forget — Hugo Nomination season is now, so if you're a member of LonestarCon, you get a chance to rectify this oversight.)