Typically Hollywood. They have a chance to nominate a movie that people actually paid a ton of money to see yet they go with five movies that nobody is going to remember in a year or two.
If you were voting for best picture, wouldn't you choose the one you thought was best rather than the one that the most audiences liked?
There is bias against genres other than drama, but frankly a lot of blockbusters aren't great and comedy and action are, I think, much more subjective than drama.
I haven't seen The Reader but of the others Slumdog Millionaire was the best (disappointed that The Boy in the Striped Pyjamas and Doubt didn't get nominated).
I also don't really like having a Best Animated Feature category given that only a very few are released each year.