Now looks look at the other side, game-centric design. Let's take WoW as an example. You start off in, say, Teldrassil as a Night Elf. You start off in a smallish quest-hub area. Everything in that little closed-off corner of the map exists "for you". Every mob, nook, cranny and cave has a quest associated with it. And when you've exhausted all the quests? You're pushed on down the road to the next quest hub. You will never need to go back to that starting area. There's nothing more there for you. There are no higher level, tougher enemies lying in wait in some corner of the map, or a dungeon that you couldn't get to because your level was too low. Other than for personal reasons, or perhaps an "exploration achievement", it's obsolete. So now you're in this new little quest hub, where everything in the surrounding area, once again, exists "for you". Every mob, nook, cranny and cave is tied in to some quest you're going to receive from a NPC in that hub. And once you're done? You're moved on down the road to the next quest hub, and this one becomes obsolete.