PostmodernProph
....fully immersed....
because we don't have Paul or Peter in church on Sunday telling us about Jesus in person......they are dead......During Jesus' ministry period there were no Bibles. Not even a single Christian text yet, nor would there be for at least 30 years after Jesus' death (or whatever.) And what would become the New Testament didn't exist until at least 100 years after-Jesus. Even then, the first Bibles wouldn't exist for several centuries more.
So if you follow Jesus (or more likely Paul) identifying as a Christian, why use a book neither Jesus nor his disciples or their followers used?