Apple has a one of a kind product and product strategy. They really do. With only ONE of its kind, it holds a lot of power, when Apple moves, carriers move.
With Android, there are so many phone manufacturers competing for space, the carriers get to move first.
And believe it or not, its the Carriers who demand the skinned versions of Android, specially Verizon, which is why for one Verizon has to approve each and every update build, and if Verizon isn't happy, they just move on with another manufacture who will happily oblige to carrier requirements [carriers require the skinned versions of Android because it helps keep product diversity up and a larger selection of pros and cons for each device; imagine if all Android phones ran stock vanilla Android? Boring.].