It adds to replayability by preventing players from memorizing the shortcuts without making it feel like grinding. Many classic RPG's have a shortest path that's somewhere between 1/4 and 1/40th the average play-though and once you get close to it the game becomes a platformer vs. an RPG. But, randomize locations and you get to relive the hunt the hunt on the next play though. It also tends to make a wider range of things useful, vs letting people optimize the effort of finding stuff vs it's usefulness.