The Quest Profile has to tell the bot to fly each time to a certain point, which only works for accepting, turnin or go to the questspot.
This is not flexible (as you see with vendor runs) and also requires the profile author to think about it and plan it and makes the profile grow in size.
Native flying eliminates the need to use "flyto" tags in a profile and handles not only running to the quest area, the turn in and the accepting of quests, but the vendor and mail runs as well.
It's getting enabled for more and more zones at the time, and wotlk is almost complete according to Natfoth.