Courts do indeed reverse some of their rulings over time based on changing attitudes, sometimes with explicit reference to public opinion in their reasoning. So

Courts do indeed reverse some of their rulings over time based on changing attitudes, sometimes with explicit reference to public opinion in their reasoning. So do regulatory agencies both independent and departmental. The 14th Amendment example is about statutory/constitutional interpretation, whereas the type of ruling we're discussing here is not. Agency regulations (and common law rulings by courts) often make policy judgments among multiple valid possibilities. Sometimes public attitudes appropriately affect the policy judgment, though of course not always. Of course agencies and courts don't make popular opinion the primary driver of their rulings, even when they consider it. And I'm certainly not suggesting they should. As for why the APA was created, that's a very complex question, but that seems more about systematizing the regulatory rulemaking process as delegated from Congress than about the difference between an independent agency and an executive department (both of which are governed by the APA). We're talking about the kind here that's supposedly independent.