Whether an area has community or .premium topos depends especially from the people who make the topos. 27 Crags doesn’t solely decide whether an area is .premium or not, and we don’t force anyone to turn their community topo into .premium. Neither no-one's community topos material is used to make .premium unless they explicitly allow so.
When it comes to big and popular areas that require a lot of work to have them up-to-date, it is better to have them under .premium. This way it’s possible to make sure that the quality is high and that the topo makers have enough resources to maintain them.