Generally, there is a splitsecond between you becoming aware of a scene, and the scene becoming aware of you. Pictures from the first half of that splitsecond tend to be better pictures.
A staged streetphotograph seems like a contradiction in terms, although i suppose one could make a case that it is like a literary device: this is a scene that could happen here, as opposed to: this is a scene that did happen here.
However, streetphotography as a genre should clearly have some constraints as to what is included and what is excluded. There should be a story, maybe even an intent, and clearly, the story may well be entirely fiction, as long as it is congruous fiction and congruous intent. Yet, the more i think about it, the story almost universally depicts a spontaneous moment or scene.