I think testimory and witness come from God and Jesus, both unchallengeable sources, telling us why we must keep the faith and what will happen if we don't. Jesus as the "faithful witness" encourages us by who He is and what He has suffered for us to fulfill the prophecy by which He saved us. Who could possibly know more than God Incarnate? Sometimes modern Christians are too worldly and it is not perceived as cool, hip or sophisticated because we live in such a materialistic society and much of the world is so detached from God.