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.
"Yes, I agree to not share internal info, in exchange for this money. And by the way, I will still share internal info, because inequity."