As an example, try searching for the phrase "high purity" in connection with OPCW's recent report on a chemical agent used in Salisbury. How many news articles will you find that link to either this page in general or this document (containing the quoted phrase) in particular? CNN, CNBC, Financial Times, Washington Post, ABC News — nope. BBC — yes, and there was also an unreadably small image of the document on Sky News.
I never thought about it, and I realize that they probably repurpose their materials from other, non-web formats, but damn! That means that readers do not generally care to see the evidence (original sources of quotes) mentioned in the news.