|Nature of the Curse|
Gluttony, Wrath, Sloth...
The nature of all curses that affect mankind is obsession.
It makes the spirits of the dead prefer staying behind as opposed to going to the goddess.
The difference is that it is the will of the dead that keeps the spirit behind while curses are forced upon by others onto you.
Naturally, priests learning the teachings of the goddesses are not permitted to use them unless it's for research.