Having been involved in a large number of interviews as an interviewer, my experience tells me the issue is that many highly-competent engineers are incompetent interviewers.

To illustrate my point, here is an imaginary example in the extreme scenario. I once spent a large amount of spare time in graph theory. So I could easily fail at least 95% of candidates by giving algo questions in graph theory. The questions are easy to describe, so they are perfect for interviews in this sense. But I would have done my team a big disservice by turning away potentially very good candidates, and I would have harmed our company's reputation.

Edit: typos and grammers