A posting goes live. Applications land in the ATS, a shared inbox, and two job boards that don't talk to each other. Somebody, usually a hiring manager with an actual job to do, blocks an evening to "get through the pile." They open each resume, skim for keywords, try to remember what the job description said, and sort people into yes, no, and maybe based on a gut read they never write down.
By resume sixty, the bar has drifted. A candidate who'd have made the shortlist at 9am gets passed at 11pm. Nobody can tell you why one maybe advanced and another didn't, because the reasoning only ever existed in someone's head, for about thirty seconds.
Meanwhile the best applicants, the ones with options, accept other offers while your pile waits for the next free evening. The seat stays open, the team covers the gap, and the pile keeps growing.