Because you need to move on with your lives. Eventually iOS 6 will be virtually non-existent and you will have to get used to it at some point unless you want to switch to Android...
Once again, why?? Is it not my device? I paid for it. FaceTime was working fine. Now, because apple wants me to upgrade when I don't want to or need to I can no longer use it. That's fair? Part of "moving on with my life" is being able to use my devices the same way today as I did yesterday, and not having to think about it. This is not possible right now.