One's own or a small instance with a few friends is suitable for people who are high profile who post challenging content. People will follow them from anywhere

One's own or a small instance with a few friends is suitable for people who are high profile who post challenging content. People will follow them from anywhere and visibility will be gained that way. Some high profile people do not want to be subject to the whims of moderators. Examples include every politician and many journalists. If you are not a high profile publisher, you will likely experience a bit of isolation with your own instance.