What kind of world do you live in where you think the employee needs to provide evidence that they are being harmed before they are allowed to seek a new job?

What kind of world do you live in where you think the employee needs to provide evidence that they are being harmed before they are allowed to seek a new job? Companies can enter into contracts with employees to prevent them from going to other employers but unless they offer some sort of consideration you are walking down the path towards indentured servitude and slavery