I am about to start work as a senior engineer for Apple with 4 1/2 years of experience, after passing two back-to-back onsite interviews with them, and I hardly have studied specifically for technical interviews. I possess an MS in mathematics.
Don't presume anything about an individual just because the person happened to not answer a particular question - the person could be actually much smarter than you. It could have just been a bad day, or a number of factors.
But then there are people for who practicaly any question beyond "lets talk in general about what you like and how passionate for technology you are" is unfair and causes black out entry single time. Thay is entirely different.
It is super important to try to ease a candidate into being comfortable to get the important information you need as an interviewer, as interviews are inherently stressful for candidates, and you almost never want to be testing a candidate's stress coping abilities.
"I dunno - they put me through this stuff, or some variant, on my way in. So now I guess it's my turn to dish it out on the people trying to climb in after me" seems to be about the order of reasoning in place behind these "methods".
† As in, was an open problem in the literature and/or folklore for years before some (now) highly respected came up with the first reasonably adequate (but like as not, overcomplicated and/out outright flawed, at the outset) solution. We know the "usual suspects" that get asked -- I don't need to list them here. But ff you genuinely think that any candidate you can (reasonably) expect to find in response to your muddled job postings will genuinely be able to solve these problems for you at the whiteboard for you -- from the void, as it were -- as opposed to regurgitate carefully practiced solutions they found from cobbling together lists of "problems Google and FB like to ask" -- you're seriously kidding yourself.
There is nothing to suggest that parent poster has bad social skills or that his job posting was muddled.
Do you know "majority of people" or have interviewed them?
Have you yourself faced an interview question at an abstraction level far below your area in this field?
Yes, I have faced questions I could not answer. I did my best and that was it. That is however not blackout - that is me not knowing the answer. Blackout is when you temporary can't recall.
But that's the thing -- it literally takes just one person out of 5 or 6 to say "I don't know about this guy" to get the rest of the team to pass. No matter if he didn't seem all that well prepared or interested in you, you guys just didn't click, or you were exhausted because no one thought to let you get coffee or use the restroom.