i might be wrong but i think either:
-the pvp playerbase is too small (compared to the pve players and casuals) for ZOS to spend resources to fix that part of the game
or
-any matchmaking changes will further extend the queue times which lead to more complaints and players not bothering with participating in pvp
ZOS cannot win no matter what they do, but clearly they dont worry too much about the pvp part of the game.
it is a shame really because thats why some people play the game.
myself personally i despise pvp in all forms but no matter what we do in eso, we are all huge fanatics of this game and we are all part of the eso universe TOGETHER!