Part of the reason is due to further msq in a later expansion actually ties into those raids. Also oh no a 25min wait for a tank. Seriously that is nothing compared to what most dps have to wait for almost anything. The only complaints people have about those raids which btw have an easier time unlocking now then when they came out is people purposely lowering their ilv to get only those raids or only ever unlocking those raids. It's the only time this happens unless at a later time you want to get you a relic weapon for the current expansion.