I'm not saying it's not useful to know or that having that knowledge might make someone a better candidate, but it seems like that alone shouldn't be reason enough to reject someone.

And I disagree that looking up the answers to common interview questions is focused pragmatism. I don't bother, even with the knowledge that it would help me get a job. I spend my time working on side projects or learning practical things. I think I will never in my life have implement a hash map, and that knowing it's all O(1) operations is sufficient. But also I guess I don't want to work for a company that is interested in my ability to jump through hoops. (shrug)