I feel it is partly due to many smaller communities having no presence here (clearly, with no magazine existing already) and wanting to make the transition as easy as possible for others. I myself have just created /m/multicopter as I didn't see any sort of fpv drone or other rc aircraft magazine. I'm debating whether or not to backfill it with link posts from the corresponding subreddits to try and kickstart it, or to only post some of my own content.