I wonder if there are only official C4 and GF files leak, why majority of servers are C6 and H5 extenders? Basiclly none C4 servers and very few of GF ones. (hope you understand my point)

I understand your point and you are right

GF has official files, but its lifespan is very short and some features demand too much effort. Plus, most servers dont know how to balance those features (HB island rate and opening for instance).

Added to it, HF is way more balanced and has more end game content, even though I dislike A-grade shops and so many instances / S+ sets.

On the other hand, Interlude chronicle is very popular because of its nostalgia and different kind of gameplay. That gap you cant see very much from GF to H5.

All other server files arent good or people arent interested in investing time, effort and money to make playable and reliable.

I believe the official files that were used on privates were C1, C4, GF, H5 and some of the GoD chronicles. All others were either extenders or l2j.