Why?

When parts of a Harry Potter Movie sucks because they missed out key scenes or they changed some scenes, why do people have a go at the Director. Dont forget the person who writes the script and makes the decision of what goes in, what goes out and changes it is Steve Kloves. And yet the Director gets the blame

Diretor is just a more visible person than the screenwriters so they get more credit when it's good and more blame when it's bad. That said, I still think the directors are somewhat to blame for the Harry Potter movies, although some of it should fall on the writers.

And I guess the director also is the one with the vision - he knows what can go, and what can't. He's the one that puts it together. To my knowledge movies adapted from books have much more director/scriptwriter interaction - as the story structure has to be totally redone to be made viable, which is what the script writer has to do, in order to allow the director to make something that works.

And then I guess there is the cutting room, where scenes go to die.