Flying enabled in Eastern kingdoms, kalimdor, pandaria, outland and northrend. But Draenor has a classic design with waystones and other items to stay mobile around that realm. Im glad they went in this direction, and i love that they stand by their descission. They listen to player feedback, but designing zones without flying isnt punishing players. Its a different approach to given content, and much like how wow originally started out.
Flying was only in outland to begin with, not the classic zones. Its been a design descission all the way, and the developers chose to roll it back. Its strange to me that so many find this punishing to players, cause what do you gain from flying other then upper hand in ganking, disconnected questing (ofcourse quests can design with flying in mind, but i mean the mobility of flying ruins quests that are into traveling of sorts), farming and freedom from revamped flightpaths. Yes, they have been tremendously improved.
As for the farming part, with no flying, resources would be distributed in a design friendly to grounded mounts.