Also just from raw corporate penny pinching. Why would they make payouts like that if they're not forced to, yes there's reputational risks of making that promise and then not following through with it but faced with a choice between that and a few lawsuits (with the usual corporate advantages of arbitration clauses and vastly more resources they're likely to win too) a corporation looking to shed people is likely to take the win of reducing their severance payouts.
In practice, the money you save long-term by reducing headcount is one or two orders of magnitude larger than the money you pay out in severance. Losing your reputation and a lot of legal fees over (basically) pennies tends not to be sound business.
There's a reason corporations almost always settle lawsuits (if they aren't dismissed).
I'm not sure the rep damage actually spreads that far and given a hard enough push the business will be more than willing to spend a little bit of reputation for survival.
Litigation is a rich man's game. Companies almost always have more resources to dedicate to litigation than individual employees, especially if those individual employees have been laid off and are now without an income.
The company knows this, the employees know this, the company knows the employees know this, and vice-versa.
A promise like that just isn't binding, things can change in 2 years, the managers themselves may have moved and been replaced with different people. A bird in the hand is worth many birds three years from now.
