I'm a daily user of Mastadon. But... People were saying this on newsgroups and gopher, then on message boards, then about Friendster and all of the social platforms that followed. If the platform becomes popular enough to reach some sort of critical mass, then that mass will drag along all of the Facebook/Twitter/Instagram stardom with it. Some people actually like their celebrities and they expect to see those celebrities on their platform of choice. And, inevitably, the marketers will follow.