They try to scope a general direction that radiates enthusiasm for the game product, and the entire game line. In short, they help generate the dream. They strive to do good works. Publishing ain't easy, nor perfect. But the editor has to keep morale up among all participants, in order that they can achieve their best work.
Editors have to radiate optimism.
They're the front line of image for the company. A totally candid editor is doomed. Oh, we'll be late, very late. Probably miss all deadlines. And it'll sell poorly as a result.