Laid-Off Americans, Required to Zip Lips on Way Out, Grow Bolder

I would imagine non-disparagement would challenging to hold up, and even less likely to be even tried. But...the possibility that they could be used to cause grief is probably enough for most people.

A more decisive legal benefit, I think, is release of claims. If a employee takes severance, releases claims, then comes back around with claims, it's a real hit to credibility. In this scenario, the company is the defendant.

In the American legal system it can be as simple as the company has lawyers on payroll and you don't. They can afford financially (perhaps not from a PR standpoint) to sue you and you'd have to settle likely just on the basis of legal expenses.