I guess to continue my analogy, that's like somebody breaking into my house, stealing my ID, heading over to the vault and successfully pretending to be me.
The shares still have value because the vault still hasn't been broken into.
If he blew open the wall of the vault and took all the shares, he'd find nobody would buy them.
He might still do that if he was running a competing vault, or hated the owner; but it wouldn't be profitable.