It's called syndicated articles, that's why you'll see the source of the original article listed and linked at the bottom of the articles. Kind of like how the same national news segment on your evening news on NBC isn't done by your local NBC TV station, it could have come from an NBC station in Chicago, Los Angeles, New York, etc. I'd venture to guess that in many cases, the article you're saying was form ergo wasn't written by them either, it was just syndicated from the original source. Pretty common practice in the news world and usually perfectly acceptable as long as credit to the original author is given.