It violates the theory of inalienable rights that implied the abolition of constitutional autocracy, coverture marriage, and voluntary self-sale contracts.
Inalienable means something that can't be transferred even with consent. In case of labor, the workers are jointly de facto responsible for production, so by the usual norm that legal and de facto responsibility should match, they should get the legal responsibility i.e. the fruits of their labor
I think that it depends on the nature of the contract. Sure, most of them are terrible.
On the other hand, NDAs are a form of employment contract that are often a necessity. Non-compete contracts can serve a legitimate purpose, in preventing unfair competition or using company secrets for person gain. They're usually written in an overly broad manner though, or prevent legitimate employee activities.
Make employment contract toward all company members, not "the company". Workers are working for each other, not owned by share holders. They are the company.