Authors all crave Amazon ratings. A string of good ratings really can establish a book. This is especially true for ebooks. An ebook with an initial bad rating will die a sudden death. If the first rating is bad then it can kill free downloads. Let alone sales.
Most readers do not give a rating. Even those who really enjoy or significantly dislike the work usually just let it pass. Most of those who do give a rating do so because the book has had an impact upon them. They try to fairly judge the work on what they got for their money. Which is fair enough and what we all want.