Here's a good question from Strykt on the forums: why does Karazhan still require attunement? Blizzard has already dropped attunements on SSC and TK, and patch 2.4 will bring the removal of attunements on BT and Hyjal. So why are we still being forced to get those key fragments and attune people to Karazhan?
Bornakk shows up in the thread and says simply that it's a good way to find people to run Karazhan with, implying that Blizzard wants guilds to help each other get attuned, and that in essence, it's not so much a gear check as a group check-- you can't get into Karazhan as a guild unless you've helped each other to get in there first. And I actually like that idea-- if your guild wants your help in Karazhan, they've got to lend a hand first to get you into the instances to get the key fragments. "No guildie left behind," if you will.
I don't have a problem with having an attunement quest to enter the endgame (and you'll probably remember that Onyxia, BWL, and Molten Core attunements are all still in the game). And it seems that Blizzard doesn't either-- they're willing to open up the later endgame as time goes along, but you've still got to get some help to enter it in the first place.