This is exactly what the company is hoping for. In actuality, you can put literally anything in a contract. Sell your first born baby, sacrifice a goat, whatever. Signing a piece of paper doesn't make it true or required.

Companies are really banking on people making the value decision that doing the legal stuff is too much work, time, and money, so they're hoping for self-enforcement. It's the same reason we still see companies commonly doing things like terminating employees before maternity leave. They know a new mother (who is now jobless) isn't going to bother with the trouble of a potentially multi-year wrongful termination suit.

From what little I know, they were reasonably well-compensated people and they were just in a position to say, whatever. I'll just take a 6 month vacation or whatever and start things anew rather than have a court fight. Which I'd probably do as well.

"Just semi-retiring" is a pretty sensible option at some point.