Well so that other people won't see only her/him. So would you send a blind copy to some one? companies lie to hack computers because they want to send company e-mail to at person. Never answer to a company e-mail because it can become a virus or it i mean they can mess up your computer because they think they can take over and you don't want that to happen. My old school had no good computers cause they always had a virus and they didn't pay attention to it till all of the computers had a virus. So you should always send a blind copy to someone.