Is it because journalists think of their special talent as talking to people to get information (which is a scarce and priviliged resource), versus reading and summarizing things that we all have access to?
So they rarely are forced to do anything but state the name of who they interviewed, and that's it. And puts them in the habit of not acknowledging what they read, as a source?
So they rarely are forced to do anything but state the name of who they interviewed, and that's it. And puts them in the habit of not acknowledging what they read, as a source?