I have come to like this approach reasonably well

“Simple problems” often aren’t as “simple” as the retrospectively sound if you consider everything like stress level, mixed mindset of the interviewee (they’re not just thinking about a programming problem, they’re also thinking about social queues, mixing conversing in, peer judgement, and loads of other anxiety inducing factors), etc. The software industry is notorious for underestimating overall complexity factors, understanding uncertainty, and time to manage them and interviews seem to be no different. So “simple” problems are often good (I agree with you) because they’re actually not so simple for most people when you factor everything in, they’re often reasonably challenging under the set of circumstances. Meanwhile genuinely difficult problems (in any arbitrary setting and longer timelines) require a whole lot of rote training and reusing little clever idiosyncratic techniques th…

You test the floor, not the ceiling. Truth is, I'm never looking for "the best", I'm looking for "good enough to do the job competently". Because we can hem and haw over what is best for hours. And we could disagree with what qualities in what proportion make someone "the best". But we can all generally agree with "could do the job". As I've mentioned elsewhere, we're hiring right now and we have the duality of candidates in our pool. There's one guy who is just a hard no from at least two people in the group. And that translates into a no from the third member simply because we're so adamant that he's not the guy. And there's another who we're all feeling really solid on. Not "the best", but solid floor and we feel they'll be able to learn. But being able to weed out people who can't even perform the basics despite having a decent resume is invaluable.

I have a friend who has interviewed about 30-40 software engineering candidates for his company (small, publicly traded company from the midwest). He said that FizzBuzz alone is enough to filter out 25% of applicants. The next slight more challenging question will axe another 30-40% of candidates. I think Leetcode hards exist to stroke the egos of select software engineers.