What do you mean here?
I'm a life-long US resident and I've never heard such a thing. I've also taken exams when applying to jobs. There is also the civil service exam which is a prerequisite for many government jobs. Jobs like the police and military have exams, both written and physical. I can't square my experience and your statement.
More likely, employers do not want to pay for additional exams as part of the hiring process and use college-degrees as a proxy. But there's nothing preventing them from using exams if they wanted.
Griggs v. Duke Power held that if a test has a disparate impact on ethnic minorities, then the burden of proof is on employers to demonstrate that the test is reasonably related to the job. The practical effect is that private employers are highly unlikely to use these tests, since doing so opens themselves up to liability, particularly since due to socioeconomic factors any fair test will have a disparate impact. For example, the tests in the particular case were a general IQ test and a mechanical aptitude test.
> I can't square my experience and your statement.
Every particular instance you gave was of a public employer, but I was careful to note that employers practically may not use proficiency exams. It's not directly illegal, and some employers might use them because either they do not realise how much liability they are exposed to, or because they have been very careful to justify them.
It actually held that for any employer-imposed hiring requirement (not merely a test), and later cases have made it clear that applies pretty much to any element of the hiring, advancement, retention, or disciplinary process.
> The practical effect is that private employers are highly unlikely to use these tests
No, its not. The practical effect is that employers doing cargo cult HR (which is quite common) are highly unlikely to use the specific tests that have been at issue in superficially well-known cases like Griggs (e.g., specifically due to Griggs, IQ tests) even when they could easily meet the test laid out Griggs but simultaneously using many employer-imposed job requirements for which they could not meet the test.
OTOH, employers that have decent legal advice regularly use tests of even the specific types that have been problematic in other cases, but make sure that there is a job rationale supported by evidence for both tests and other requirements in case they are challenged, because that’s the thing that actually matters.
Proficiency exams are exceedingly common (heck, when I did clerical temporary work for a while, it was pretty much the entirety of the hiring and placement process.)
Tell us you grew up in an middle-upper class environment without telling us you grew up middle-upper class.
In the U.S., this is due to the fact that employers practically may not use proficiency exams; since they are prevented from testing for actual proficiency, they must use a proxy, and a college degree is a decent proxy for 'reasonably educated enough, exposed to enough general knowledge, knows how to function in a group.'
I don't think that class really enters into it.
> the fact that educational debt in America can never be voided through bankruptcy seems like a conscious systemic decision to create debt slaves.
More that without the inability to discharge it in bankruptcy interest rates for student loans would need to be sky-high: the smart move for anyone graduating at 22 would be to immediately declare bankruptcy when all he would have is debt and no assets.