If you have a communication line open with someone for some sort of transactional activity, you do not just drop off into oblivion. Ever. It's rude and disrespectful, full stop.

Yes, I agree that the interview process can be a numbers game: candidates should apply to many opportunities that fit their skills, and expect no interest from nearly all of them.

But if a candidate has received a response, and there's any kind of open dialog, no matter how minimal, then out of a sense of basic civility and respect, they deserve a reply, even if it's just a canned one-liner rejection.

That's the only decent thing to do. Anything else is disrespectful.