Earlier today I was skimming through the World of Warcraft 2.4 Pointer Test Realm (PTR) when I ran across the following:
-Players will no longer require an attunement quest to enter Hyjal.
-Players will no longer require an attunement quest to enter the Black Temple.
-Players who have completed the attunement quests for Black Temple and Hyjal will be granted the title of “Hand of A’dal”.
The first thought that ran through my mind was that of disappointment. I had already done these quests and now I didn't need to. However, the more I considered what they were doing, the more at ease I was with the whole situation. Even if the attunement quests are not required to enter either raid instance, that doesn't mean that everyone and their mother is going to just jump into Black Temple. Those that do jump into Mount Hyjal and The Black Temple will want to complete the attunement quests, since they are still required for the reputation rewarded gear that you get from these instances.

So the question posed is: Why would Blizzard, or any other MMO developer for that matter, would create an attunement quest line, something that is required for a player to get into a certain instance, or place in the world, just to change it later? The answer is actually quite simple. Sometimes, the playing field needs to be leveled so that the newest and greenest of players can have a chance to catch up to the old school guys. Fresh blood is always pouring into MMOs and to keep those new players interested in the game, and not become overwhelmed with all of the catching up that they need to do, sometimes a developer may choose to change how things are done.
What turns a lot of prospective players away from MMOs is the feeling that they are required to invest large amounts of time and energy to progress in the game. Blizzard has done a great job of dispelling this idea, in many unique ways.
Since your average player is now trying to rush to level 70 to experience all of the content of the expansion pack (The Burning Crusade), they are skipping the instances of Azeroth. What Blizzard did for this was two fold. First they updated the loot tables, that is, the loot that drops in an instance. As early as Scarlet Monastery (Level 25+) players will be able to obtain epic quality loot, which before the expansion, was literally unheard of. This gives new players, and old, a reason to tackle these instances. Apparently that wasn't enough, because Blizzard then went and changed the way characters gain experience, which lets a character gain levels. At level 20, players will start to receive more experience than before for quest turn-ins, and will also need less experience to level their character. However this bonus does end at level 60, where you are leveling the same as any other player.

Now, you are a fresh level 70 player, just “dinged”, and now you have no idea what to do. As stated before, you can't just jump into Black Temple, successfully anyways. What is a young WoW player to do? Blizzard made this just as easy. Players are now able to obtain epic quality PVP (Player Versus Player) gear and weapons, which will greatly improve their character. Even if PVP isn't your idea of a good time, there are always Heroic badges, which are obtained by killing a boss in a heroic instance, or completing the Heroic Daily. While yes, Heroic instances are noticeably harder then their regular counterparts, the fact is that this is an easy way for some characters to gear themselves out.
Now, what if PVP is your thing, what then can you do to catch up to those PVPers who have been doing it for a year or so. If this is the case, then a player can join a Battleground, where like minded PVPers are fighting each other. The player will then earn honor points based on the game they are playing and how well their team does. Once a player accrues enough honor points and enough battleground marks, which are given out at the end of a battleground, one for the loosing side, and three for the winning side, the player can then spend the marks and honor points on PVP gear. What makes this even easier is the fact that any level 70 player can join an Arena team, where they can face other arena teams in gladiator like combat, where the team holds a rating and is given a certain amount of points each week based on their rating. As you have probably already guessed, these points can eventually be spent on gear for a player. This allows those have just started their PVP/Arena career to actually be able to compete with those that have acquired the latest seasons arena gear.

Since players are now racing at amazing speeds to 70, they aren't doing the grind to get the old school formulas and recipes for their chosen professions. How does a new player acquire these mentions items, almost the same way that the old players did. Before the expansion came out, people would spend days, if not weeks, grinding out a certain factions reputation to be able to purchase items. However, if a new player decided he wanted to grind the same rep, he would be penalized for being too high of a level for what he is fighting. This would extend the time it took to get that needed reputation astronomically, so Blizzard also made the recipes available from the factions that came with the Burning Crusade. Now new players still need to grind that rep, however they aren't being penalized for it.
There are many other examples that can be cited, however, by now the point has been made. Sometimes to help the newer players in a game catch up and actually be competitive against those that have been playing the game for a while, game mechanics need to be changed in favor of these new players. Without this assistance, your average new player in a well established MMO is quickly and easily going to become overwhelmed. An overwhelmed player is going to quickly become a frustrated player, one that doesn't want to play anymore, and this of course makes us all sad pandas!