An employee is free to resign if he would prefer to work for someone else. He can't be sent to a gulag. Customers aren't forced to accept a company's product or service, and can choose a competitor instead. Managers can fire incompetent or insubordinate workers. Customers can criticize a product without fear of being shot.

Customer, manager, employee, investor -- everyone is in the situation voluntarily, so they must negotiate on the basis of mutual self-interest. The company as an entity is more stable because its constituents aren't essentially at war with one another.