My guess would be that most of these people are good employers who do not mistreat their employees. Money can only go so far to ensure loyalty. If you're working for a famous family, if family invokes the punitive liquidated damages clause, the employee is effectively released from the confidentiality clause and could, for example, write a tell-all book. It seems like the system works to everyone's benefit; the employer gets loyal employees and the employees get a good job with high pay and security.