I doubt there was ever a time when fiction and non-fiction were ever truly separate forms of writing, but there was a time when it was considered the norm to try. Parajournalism, using fictional techniques to set up a non-fiction story wasn't considered real reporting. Walter Cronkite's “You were there” series was a teaching tool, not reporting. Michael Moore's “Roger and Me” was an art film about the emotional impact of GM's outsourcing not a report on the outsourcing itself, Tom Wolfe's books were rightly considered fiction about real events. I don't even want to get into “fictional memoirs”.
Fiction used to have Donnee, or an unwritten assumption, and looked out from the main characters worldview even if the character was flawed or outright deranged. The trend is now towards standing back and watching the main character, more like a movie camera following the action than the writer being god of the world they have created.
Now reporting has turned into the host telling people of their opinion and using the guests as props and in fiction the omnipresent voice is considered bad form. So the tones have completely crossed to the point where fictional situations are viewed objectively and actual facts are viewed subjectively.
The reason is laziness. In reporting it's easier to form the story first and pick out the facts that support the story than to go through all the facts and find the story. In fiction it's easier for the reader to follow one voice than hop in and out of people's heads and have someone speaking over their shoulder as well. It is really easy for an writer to leave the reader baffled as to whose head we are in.
So to all the parajournalist and arm's length writers, I say, “Going the easy path is a fine start, but reporting and writing are professions that means you must be constantly improving your skills. Reporters have to learn to report not give editorials on the events and writers need to learn to write, not report the images they see in their heads. It's not easy but truly worthwhile things in life never are.”
By Darrell B. Nelson author of I KILLED THE MAN THAT WASN'T THERE