Well, what if there's an emergency and I lose them? It's also good to know how to protect others without any magical abilities.

[ Besides... ] A priestess ought to know how to use one, anyway. Swords can be sacred to us, gifts for the shrines and gods from masters. They also can be used as tools of purification. Using them to sever the evil out of a spirit-- cutting away the ayakashi-- would allow for that spirit to remain just as naturally as it should be.