Coz producers (project managers) probably have more say in storytelling?
Having dedicated writers is mostly an RPG phenomenon, anyway, if you look at other genres most of the writing is done by people in the project management sector (I think the Force Unleasheds were a pretty good example of this). Besides, since they are talking about cinematics, cutscenes etc., it's more like asking the "movie director's" opinion over the "screenwriter's".
Well true. That doesn't really apply in some of these cases though?