MMO isn't single-time single-player game, where whole game is about exploring, navigating, solving puzzles, finding secrets. It's long term game. You play it for weeks, months and years. When you do the same quest/WQ for 100500th time - artificial obstacles become annoying and drive you away from game.
The best example - compare it with riding to your work through rush hour traffic jams. What would you prefer?
This?
Or this?
Your job - is what matters. Your route from home to your job and back doesn't. Because you do it every day, so you suffer from "cookie cutter" effect - you no longer notice, what's around you. You just want to get to place, that matter to you, as fast, as possible. That's it.
What bugs me, is that many players, who play MMO, are people without imagination. What they do in fantasy world - is the same, they do in real life. We are so limited in our real life. We want to have more opportunities. But all of a sudden when fantasy world allows us to do it - we reject it. We want difficulties, like if our real world wouldn't provide enough of them. I just can't understand it.