People tend to forget or ignore that 3-4 of the most used GNU social instances were handled by the GNU social project maintainer. I think it's normal to try to ease the adoption of the technology, and let people choose what to do thereafter. "Refugees" from centralized services usually don't want to learn about instances and decentralization just to begin using it. They just want to sign up and start interacting. From what I read, they often move to other instances as they mature.
Server run by the main developers of the project It is not focused on any particular niche interest - everyone is welcome as long as you follow our code of conduct!