I run a website that helps consumers to resolve complaints with businesses. Our data shows that more than 70% of our users have tried to reach out to the business directly first.
What can you learn from this? Brands get negative reviews because their customer service fails to deal with complaints.
That said, according to Hug Your Haters book (Jay Baer), more than 40% of Millennials prefer to reach out to brands using social channels. This means that brands who don't offer great customer experience run the risk of getting negative reviews.
However, if brands would get a fair opportunity to fix the issue and interact with the customer _before_ they get rated, the ratings would look very different. Here's a case example.