90% of why employers do that is that we functionally outlawed intelligence testing of job applicants, so they instead outsource it to an extremely expensive alternative.
No, we didn’t, in fact, the ruling that is misrepresented that way has exactly as much effect on degree requirements (insofar as degree rates are also racially disparate) without evidence of job performance need as it does for IQ tests.
But, “IQ tests are functionally illegal and degree requirements with no evidentiary basis are fine” is management/HR cargo cult knowledge, which is the real issue.