Here's why I will never join a site like Mastodon.
1. It's not centralized. And centralization has the great benefit of everyone and everything being connected. I went through all this hoo-ha when Google Plus said goodbye. I tried these decentralized servers and disconnections. Thank you, but no thank you. Unless you have a large following, all of whom would love to join you, you inevitably lose most of them. I had 38,000 followers, and they all went their own way.
2. My experience on the web, and I've been here since it had 3004 sites, is that people want to be where other people are. They seldom blindly follow other people. One really has to be exceptional for them to do so.
3. I don't want to be where there are only a few poeple. I will stay on Facebook and on Twitter. It's where everybody I know is.