In some cases (many, actually), you have to sign a contract to get your severance, and there's often a "non-disparagement" clause in there.

I also feel that it's just good common sense, too. Even if we are incandescent with rage, it's usually considered "unprofessional" to descend into name-calling. If others see us as "unprofessional," that can have negative impacts on our careers. It's usually just safer to be noncommittal. Doesn't cost anything, and likely saves a lot of heartache.

I'm fairly saddened at the reactions to this post. It did not prescribe anything that would really cause any harm, and is a basic "everyone knows this" aspect of relationship-building; done so, for centuries.