Because books have a tendency to slip ideas in the back door when the front one is locked. Why do you think Wiccanism, Paganism, and Witchcraft are on the rise?
SORCERER; PROPHET; WIELD SUPERNATURAL POWER; CLAIM THAT THEIR POWER IS THEIR OWN; RECOGNIZE THAT GOD IS THE SOURCE OF THEIR POWER; ALWAYS OPERATE WITH SELFISH INTENTIONS, EVEN IF IT TAKES ON THE FORM OF HELPING OTHERS; USE THEIR POWER ONLY FOR GOD'S WILL, NEVER FOR SELFISH GAIN; ARE OFTEN MISTAKEN FOR ONE ANOTHER; MIGHT OR MIGHT NOT USE EXTERNAL PROPS IN THEIR WORKINGS OF POWER; ALWAYS HAVE A SET FORMULA FOR SPELLS; ALMOST NEVER HAVE A SET FORMULA FOR MIRACLES