As someone who has done a fair bit of recruitment, this drives me bonkers. When I've done recruitment, we let candidates know in 2 stages. If they're not shortlisted for an interview, they get notified that they've been unsuccessful at that stage. For those candidates who make it to interview, we then notify the unsuccessful candidates as soon as we've spoken to the successful candidate, usually only a day or so after the interview. It's really not that hard or time-consuming - it's just a standard email we batch-send. This was even during Covid19, we did a recruitment exercise a few months ago at the height of it and still made sure to notify all candidates in a timely manner.
I'm applying for jobs at the moment, and with nearly all of them I never hear anything back. It just seems to disappear into nothing. I obviously assume that I haven't gotten it, but it's so frustrating as many of them take so much time and effort to do, you'd think they could just send an automated rejection email. I think it's just sloppy practice. My mum has also been applying for jobs and three weeks ago now she had an interview, heard absolutely nothing since. I've even tried following up via email with the listed contact for the job, again absolutely nothing!