A large part of American non-fiction is written in scenes, with characters and suspense, and it is reported specifically so that it can be. The technique precedes the writing.
Argument is harder to remember than sequence
Readers hold onto what happened to whom far better than they hold onto a claim supported by evidence, because a sequence gives each fact a place to sit.
Writers who want an idea to survive past the last page therefore attach it to people making decisions under pressure rather than presenting it directly.
The argument is still there, but it is carried by the events rather than stated over them.
Scenes have to be reported into existence
Writing a moment in scene requires knowing the room, the weather, who spoke and in what order, which is a much higher evidentiary standard than summarizing the same event.
That is why this kind of book takes years. The reporting is aimed at reconstructing detail that a conventional account would never need.
Sources are interviewed repeatedly for exactly this reason, and documents are read for physical particulars as much as for facts.
The rules are stricter than they appear
Novelistic technique does not license invention. Thoughts attributed to a person must come from that person, and dialogue must come from a record or a participant's account.
Serious practitioners publish notes explaining where each reconstructed passage came from, which is the mechanism that keeps the form accountable.
Where that discipline slips the book becomes vulnerable, and disputes about non-fiction usually turn on these boundaries rather than on major facts.
Structure is chosen before drafting
A reported book has more material than it can use, so the writer selects a spine, often a single person's experience, and hangs the wider subject on it.
Choosing that spine is the decisive editorial act, and it determines what the book can explain and what it must leave out.
Editors and agents evaluate proposals on this choice more than on the topic, because the topic alone does not indicate whether a book exists.
The form travels well beyond the page
Books built in scenes convert readily into documentary and dramatic adaptations, since the structural work of finding characters and a sequence is already done.
That secondary potential is part of what publishers weigh when acquiring, and it influences which non-fiction subjects get funded.
The market pressure and the reader's memory point in the same direction, which is why the technique has spread across so much of the category.