It seemed to me that the author was claiming that people copy existing documents on computers only because it's the only (or easiest) way they know of to create

It seemed to me that the author was claiming that people copy existing documents on computers only because it's the only (or easiest) way they know of to create a new document of a given type, not because it is actually the easiest way to create a new document of a given type. It seemed to me that the author was decrying the fact that so many people copy existing documents and delete all the contents, and was providing that as justification for why the New menu exists.