The Role of a Social Media Manager

I don't think there is a clear definition of what a social media manager does and I'm not really sure there needs to be because there's so many different types of social media managers. Just with every platform, as platforms are growing, Twitter used to be so simple, right? You couldn't even post photos. Now we're seeing platforms really broaden their scope and expand. And it's kind of deaf by a thousand cuts for social media managers of what they need to do.