Because each Division is administered by a Division Committee. The Division President, who is a General Conference officer is only one voice. It is a powerful voice, but that voice is not all-powerful. When the "crunch" comes the Division President may be able to "moderate" an action or proposal, but not totally do away with it.
Why? Because EGW wrote against "kingly power" in very strong language. That is something that our current GC President subscribes to. He has a history of accepting the actions of committes with which he disagrees. He may attempt to establish committes that are constituted with people who are likely to agree with him. But, he cannot always do that. He accepts commitee decisions.