Could somebody please explain to me

Referee's have microphones and headsets and are linked up to their assistants and regularly talk to each other. So why then when there is a big decision to be made does the referee run over to the linesman and then hold secret hushed discussions with their hands over their mouths?

Why is there all this secrecy? What are officials mumbling to each other that they do not want the world to see? Why do we bother with mics when they are ignored by these incompetent officials?