I agree that GPA is no indicator of success in life but it indicates a basic discipline to do things assigned to them. Companies setting a bar of 70% in colleges is a good indicator of social acceptance of this.
Again companies as is society is a group which requires people to adhere to norms/rules to move in any direction.
Any major success is usually one of those where people break these rules and society finally accepts them. Ex: kejriwals initial euphoria with people’s governance .
A person who has limited academic sucess and shun by today’s so called academic society is more keen on breaking the rules and proving it than a topper with a settled job.