A) Yes, ratings are for readers, not authors, so turning ratings on is a benefit of readers (and a way for them to find you).
B) I don't write for ratings, but I monitor them. Only, I don't worry about scores, instead I look for the changes in the scoring between chapters. Readers are quick to alert you that something isn't popular in the immediate ratings. But other than that, they could score you on dozens of different criteria.
Like you, Harry, I have a LOT of '1-fans', loyal fans who rate EVERY story I write as a 1 vote. Not only do they visit each story, but they do so within days of the original posting. I warned them that by doing so, they can't protest beyond their 'worst story ever' rating. It didn't impact their views, until I realized another chapter they hated. Now they all score me either 3 or 5, just so they can adapt down OR up (popular chapters will nudge their scores up 1 point, while ones they object to will knock it down 2 pts).
I also pay attention to 'quit letters' (ex: "I LOVE your stories, but I had to quit reading this one because ..."). Whenever I get one, I immediately reach out to the reader. While readers like to congratulate you on good writing, most are reluctant to tell you about problems. Usually, a Quit Letter writer will tell you about something you should be aware of, so you can counter it within the story itself.