I remember the devs originally saying that SoO would not be a completely linear path of bosses, but obviously it's that way. Why is Thok a mandatory boss?
He's all the way on the far east section of the last area of SoO, he holds no key and blocks no machinery to open the other doors. He's there as a prize of Garrosh, 'This is a big mean animal, you must kill it before he lets it loose on you.' As it stands, it poses no real danger to the raid and could be considered a 'mop up' operation.
Spoils I can understand, you deny the enemy access to weaponry that he might use against you. A huge dinosaur that breaks out of his cage is not a weapon. He serves no purpose in preventing you from continuing except by being completely out of the way in a location no one would notice, and everybody would ignore.