I completely agree Chaunce 'Red' Dolan, I’ve been guilty of these as well but only more recently have I come to understand how the hiring team feels.
I also think you’re right about the feedback loop. I wish it happened more frequently and it’s really sad that it doesn’t happen when you’ve asked. But I wonder if I might add some perspective:
In may cases there’s nothing wrong at all. There may have just been another applicant who’s past positions, specific project, life experience or specialty skill seem to provide a better fit. In these cases it’s difficult to provide constructive feedback when it really amounts to “be a different person”.
Additionally, we all seem to wait to hire until we’re completely overwhelmed and sinking. That means whoever is doing hiring or interviewing is still super busy even after having an offer accepted and, speaking from experience here, may have just dropped the ball on follow ups. I personally, wouldn’t be offended by a follow up a few weeks later. That may not be true for everyone but in general I don’t think people are intentionally being jerks.
Other possibilities include reaching out to other applicants being against HR policies or feeling like you’re somehow second guessing a decision by reaching out/replying to inquiries.
If I’ve learned anything its that landing a job really sucks from both sides of the table. Like any relationship, applicant’s and managers both go on a rollercoaster of emotions and second guesses. Its just hard and complicated all around.