What stops employees from sharing secrets to their new employers?

Like illegal drugs and many other behaviors, it is widespread that secrets walk out the door with employees and also that employees, vendors, consultants and other people will "talk" and reveal secrets to others.

I had a business partner that was really great at getting this kind of information and we knew what kind of database a three-letter agency was shopping for, what a notoriously secretive hedge fund was doing for business continuity, etc. Had we sold the information we might have had a great business.

People sometimes get sued for violating an NDA but like many other "crimes" (say speeding) people don't usually get caught, it is hard to prove, etc.

I wonder if the lack of human rights in China makes firms like Apple more likely to settle there. Think of this story

https://thebettervacation.com/palace-of-versailles-hall-of-m...

NDAs you sign when leaving. also, most employers do not want to hear any secrets of their competitors. that puts them at high risk for litigation.