@rufustheduck That's the generic, big picture why.
Benefits of being on mastodon.social for you:
Biggest view of the fediverse, developers very much focused on your server, unlikely to shutdown, a 'little bit of everything' experience.
Downsides of staying:
Too big for thoughtful moderation, no particular relevance to any specific hobby or interest, too large for the local timeline to be anything other than a firehose of random conversation fragments.