Because it’s none of their business. An interview is there to evaluate a candidate’s suitability for a role, not to dig into their personal life. What they did at work is relevant, what they did when not working is private. You wouldn’t ask what someone did on a Saturday night.
Maybe they were sick, maybe they were pregnant, maybe they were looking after a dying relative, maybe they were backpacking across South America, maybe they were sitting at home watching every episode of Star Trek, what people do in their own time is a private matter.
That is correct, which is why the hiring atmosphere reeks of ageism. There's a lot of people in this industry that are over 40, healthy, of sound mind, and have a tremendous amount of knowledge and experience that are being overlooked because they're supposedly "not agile enough" or whatever.
When you have 168 resumes to skim through, you can “afford” to just pass on this application and choose some others to interview that would be less offensive to office sensibilities. The impact of accepting so many false negatives is difficult to quantify because you don’t know which ones would have truly been good fit.
I suspect that among the hundreds of discarded resumes for a particular role was a candidate who actually believes in the company, would have been fully engaged with the work, and made a serious positive impact on the company’s success.
