if the "simple questions" are realistic problems they might face day to day, fair enough. But the classic example in these articles is an exercise like invert a binary tree, which most people never have nor will need to do, making it a poor test.
That doesn't mean that someone would be unable to program it. Inverting a binary tree tests if you know how to traverse a tree. I may not traverse trees all day at work, but I can easily do a tree traversal if I needed to and I expect that to be true of most people who can actually program and not just talk the talk.
If you really really care about me traversing a graph, leave me alone with the task for a while, let me take my time, give me access to the internet even. Why do you care that I can write it on the spot? If anything that just proves that I memorised it just before the interview, not that I actually had to think much about it