Hmmm... Maybe they don't think of them as humans? Could be some ethics involved, too, since they used to be people, but now they aren't.

[It's... a delicate issue, and especially for children, might bring burdens if they're forced to deal with the fact that their new teammates aren't just tameable monsters.]

Could just be laziness, too, though. I mean, it's not that hard to find a Psychic type to interpret.