I don't understand why you put "lie" in quotes. Even if you believe it is done for a good reason, it is most certainly lieing.
You have a wide variety of choices as to what to tell your child that doesn't include lieing. You can celebrate the loss of a tooth as a positive step of growing up without telling a lie about a creepy fairy that sneeks into houses and collects teeth.
Adults may rationalize to themselves that they lie to children to protect the children, but I think it is often more motivated by the adults' desire to avoid having an uncomfortable and difficult conversation.
You have a wide variety of choices as to what to tell your child that doesn't include lieing. You can celebrate the loss of a tooth as a positive step of growing up without telling a lie about a creepy fairy that sneeks into houses and collects teeth.
Adults may rationalize to themselves that they lie to children to protect the children, but I think it is often more motivated by the adults' desire to avoid having an uncomfortable and difficult conversation.