Yeah, and lots of people eat junk food despite the nutritional labels. But no one in their right mind would suggest scrapping the those labels. We should always push for more information for consumers.
I think with news we have a benefit that it's generally all online, so we can link to the rating page and further link to the places where they failed. Unlike a nutrition label where you have to like buy a mass spectrometer to verify their accuracy, with news checks you can view the failed checks and links to the articles that caused them to fail and verify it yourself. But that does require the checks being really basic; things that could be open to a lot of interpretation wouldn't work, cause folks could then argue the interpretation is biased.
It has a noticeable, immediate effect.
Accuracy ratings for news would just make people say your rating is biased, I think.