Well it's not just quests. It's collecting 100 treasures, getting every faction to Revered (which are still blocked by dailies, though you can buy the medallions if you're a high roller), exploring every zone, completing the story questlines. Collecting 100 treasures can be a real PITA when you don't already have flying. I expect they will eventually make it easier, maybe with an item you can get off the BMAH like the old grimoire of the four winds or with a new achievement geared at current content.
When Blizzard created the WoD zones not only did they say "Hey, removing flying from a game that's had it for the last ~10 years is a great idea right?" but they also said "Heh heh heh... let's see how terrible we can make getting around on the ground as well!"
Do you remember not having flying in WoD? Holy shit it was terrible. "I think I can get up this path to where this quest is. Wait what the fuck? It's literally right on the other side of this little hill that I can't fucking get over! I have to go all the way back down and around? Why the fuck was there a path leading up to here?"