Good storytelling elevates a cinematographer's work. When a director knows what she wants before the camera rolls the cinematography becomes purposeful. Instead of finding shots that relate to the story, the camera person is composing frames that are vital to the story.
Of course knowing the story in advance is the domain of scripted drama. It is a near impossible task in most documentary filmmaking and is especially frowned upon in its sub-genre, vérité, where the idea of composing anything is seen as staged and therefore inauthentic. With documentaries you have a sense of the story before you start shooting; however, it is during interviews where story is truly revealed. This is what many documentary directors love about the genre. The surprises or discoveries along the way.
This is always a challenge for the cinematographer who is constantly adapting to uncontrolled situations with the expectation to still deliver beautiful images. Vérité documentaries further compound the challenges, making it almost diametrically opposed to good cinematography insofar as it eschews any control over the image, beyond what the camera and operator are capable of. Lighting is "available", camera support is off the shoulder and there is generally little consideration given to how the people being filmed look or where they are. These are real people in real locations and it is all happening in real time. It is authentic filmmaking.
And yet, as a viewer, I don't care how authentic the filmmaking is if the lighting is harsh and the camera moves are shaky, the framing prosaic. My attention is distracted by those shortcomings and I am immediately pulled out of the story.
It doesn't always have to look pretty, but it can't mostly look ugly. So I often advocate for narrative filmmaking elements to be added into documentaries. Errol Morris is a master of this style. And for those directors who bristle at the thought of "staging" something like a re-creation, my thought is that if the emotion is truthful then why not?