Board Thread:Skyrim/@comment-11276487-20130706234318/@comment-4057437-20130722005811

We don't see how Alduin could be used as a central character other than as a foe. He doesn't seem inclines to partner with anybody. Even dragons just served him, none has been singled out as his right-hand Dov.

That would limit the game, not allowing choices like the Civil War and Dawnguard did.