You're correct in that there is no law saying that employers are prohibited from disclosing why a person was fired. But the policies are a result of laws that could open them up to legal action if they were to disclose any specifics. However unlikely that legal action may be, and probably even more unlikely to succeed, they still gain nothing from any such disclosures so it makes perfect sense to prohibit them.

Exactly. Any such disclosure gives a foothold for legal action that could drag on for a long time and cost a fortune. Even if you win, you lose, so why take that risk?

It's not that simple. Arbitrary firings are bad for morale, so it's in management's interest for the remaining employees to understand what happened.

In my experience, remaining employees generally understand what happened without the company having to disclose exact reasonings. Especially publicly.

Employers airing dirty laundry is way worse for morale. Typically the people who work in close proximity have a good idea of why their colleague may have been fired, or can reach out to them privately to get details. If the fired employee doesn't want to talk about it, it's presumably something private, and the employer probably shouldn't either.

> AIUI, most employers simply do not disclose details on firings as a matter of policy, not law.

Note that this isn't true in much of Europe, where in many countries firing someone beyond their probationary period requires due cause. I kinda suspect this is largely a function of at-will employment?

There is to be a cause, but there is no need to broadcast it to the world. The specifics are mainly a matter between the employee and employer.

It's not a legal requirement, yes, but any competent HR person or attorney will tell you publicly telling everyone in a company or on a team why someone was fired is a huge liability and will almost certainly result in a lawsuit after it happens a couple times.