I can imagine some harm comes from this - e.g. an employee is mistaken for a model, or perhaps an employee is never mistaken for a model, but the magnitude of the harm doesn't seem so severe, and seems comparable to the benefit - the party is more fun.
I know why people have an intuitive dislike for this, it calls to mind paying for sex, sounds pathetic, and feels possibly misogynistic, but logically, I can't defend any of those positions myself.