It's like the girl you don't want to date. You just tell her "it's me not you" rather than tell her what's wrong with her, which would be downright insulting. OTOH, the one you like you can end up courting her for months putting up your best side. Now imagine you're extremely eligible and get a lot of suitors--you tend to develop a knack for diplomacy, and the lesser said the better. Also imagine if you had to sit down with each rejected suitor to explain why they were rejected.

If a corp were to have dialogues with every rejected candidate it would take considerable effort with little to no ROI.

My understanding is that the legal departments at companies require interviewers not provide reasons for not making the hire, so as to not inadvertently expose the company to hiring malpractice lawsuits.

A decision will be completely legitimate and within the bounds of fair practice, and the rejected interview candidate could still bring a case against the company, costing time and lawyer fees.

Also, from a practical standpoint, should the interviewer see 50 candidates for a position, it's a full-time job just writing the "this is why we didn't pick you" letters.

How about ignoring their requests for feedback and doubling down on your own?

You make it sound like the only option is passive acceptance.

Two reasons that make this difficult:

- It is difficult to double down on feedback requests when they stop returning your calls and emails after the generic rejection pablum

- One is hesitant to do the same to them (ignoring their requests)

Fundamentally there is a difference in the power relationship here, in my opinion. A typical company can and is able to afford to treat candidates badly but I don't believe that a typical candidate enjoys a similar luxury.