I asked some science journalists about this on Twitter. Tight deadlines are a problem, but the bigger issue is that there’s some sort of journalistic principle about not letting “sources” see—-or approve—-the completed article.
I don’t totally understand why, but I think they were a little unclear on what most scientists want, which is more like checking language and details (a lot of words that seem synonymous aren't in technical contexts) than controlling the overall message.
Newspaper comment sections are highly problematical. You have occasional thoughtful posts mixed in with hundreds of completely moronic, bigoted, and deeply stupid posts. When a comments section gets bad enough that it demands moderation, perhaps it's better to get out of that business entirely. (No need to get rid of the letters to the editor.)
If the journalist talked to the expert while writing the article, the expert will always be happy for a chance to sanity check. The only reason that's so often not done is because the journalist is on a power trip.
