Laws are different in different counties, and I can't speak to all of them, but in the US, the law said you could only sue people, and the courts realized this was a problem. Rather than saying "I guess corporations get are exempt from all liability until Congress gets around to fixing it", they came up with a weird workaround that lives with us to this day.

EDIT: Note that ianal, nor a historian. The specifics of how this came about are best learned from a more authoritative source.