I see where you're coming from. I think the issue is that 99% (100%?) of all HNers would likely be great hires for most companies, so they see these questions as trivial, dumb, and not representative. Just the fact that someone thinks about these types of questions and reads programming blogs probably puts them ahead of most of the programming population.

The problem is that many of us have really never seen the mythical horrible programmer. The person that really can't even start a solution to FizzBuzz. The one that leaves the interviewer wondering how the person got jobs at other companies. I have seen and interviewed them before and it's frightening and uncomfortable for everyone involved. I've had candidates break down crying when I asked them to write a simple sql select statement on the board because their resume said expert in sql. For many, it's hard to fathom these people are out there, but they do exist.