Actually this reminds me of the answer I put down on a recent Algebra exam. My mind had just about turned to jelly at this time, and it was one of those if X = Y, and A = B, it is true that D = A, WHY? or something like that. I just wrote down I can only assume you are looking for something other than "because", but that is all your going to get on this one. (And then of course I added a little smilely face.)
But that is basically what you get when you ask questions about the Society. The answer to your question is "because" this is the way we do it. God told us to do it this way....but remember, we are just spirit directed, not inspired, so we might not have heard him right.