Why do characters in RPG's (Console games.) always move their limbs, even if they're just standing there?

I’ve always wondered that. In games like Final Fantasy IV or Secret of Mana, characters always move their hands and feet repeatedly, even if they’re just castle guards standing around.
Don’t get me wrong, I think it’s the cutest thing ever, but why do so many older RPG’s have that? There must be a reason?