The point is to demonstrate capability, not "penchant". I mean, look, subtle code happens. Maybe it shouldn't. But it does, and it has to be fixed. There was a story here just a few days ago about some Project Zero work to find a bug in Chrome that involved a state machine with something like 50+ states! And realistically finding people who can do that requires that they be able to also do things like traversing a binary tree, right?

So I'm going to ask the question one more time: if you won't traverse a tree in an interview, how else do you propose to select for people able to reason about that kind of problem in practical code?