You're thinking about employment contracts like an abstract economic exchange between two free parties, which is very micro. Try thinking about it instead like

You're thinking about employment contracts like an abstract economic exchange between two free parties, which is very micro. Try thinking about it instead like a bargain with the (macro) devil. In other words, consider someone's perspective who has society split into two camps: the people who do all the work, and the corrupt elite that make their living through theft and oppression. In such a world, signing a contract with an employer (i.e. capitalist i.e. elite) is more of a practical step than a sacrosanct bond. There's a level of "what's reasonable" and "what legally enforceable" beyond the basic "never break a promise" level you're working at, IMO. No ones endorsing publishing trade secrets randomly, but you're treating all disclosures like they're equivalent.