It would be kind of pointless to allow you to take out the quest markers if the NPC's did not give out enough information to complete the quest without it or what is the point of being able to remove it? Some sort of prank?
Maybe if you don't feel like doing any quest at any given moment you can turn it off?
If the npcs give good enough directions so that i don't even need the marker or have to wonder aimlessly to find the quest locations ill be very surprised. Especially considering this game is focused on voice acting, and has generated quests based on where i have been, what level i am etc. Although there are 70 or so voice actors involved in the game so i could be wrong.