I agree with you that a lot of SE interviews are frustratingly pointless, but I disagree that coding challenges alone are adequate. A very important aspect of being on a team of engineers is collaboration, which often comes down to solving tough problems as a team at the whiteboard. I spend maybe 5% of my work time doing this, yet it's some of the most efficient use of my time - the hour I spend fleshing through an idea with a coworker often saves me 10 hours meandering through a problem on my own.
Interviews are not collaborative. They're intensely hostile experiences, even when interviewers are trying hard to be nice (many don't). It's silly to suggest that a job interview is a venue to evaluate how a candidate collaborates.
Admittedly, I don't have a huge interview experience (on either side), but that hasn't been my experience. Apart from the implicit pressure of the fact that you are being evaluated, most of the interviews have given me the impression that the opposite party are really trying to learn about me, not putting me through a hazing experience.
