It's well publicized what to expect at interviews for these firms. It shows that you're willing to put in the preparation to make it work. In addition to putting in the work of memorizing the algorithms, a candidate needs to know how to apply them, and to write code, and to accept feedback, and to collaborate and communicate.

If a candidate isn't willing to put in the work to prepare, it's not much of a cognitive leap for me to envision them telling me that implementing this or that feature is dumb, impractical and not needed. Many developers have this "start with no" defeatist attitude as their default position on most problems of moderate complexity, and it's a real problem. Given a chance to select for candidates that instead figure out a way to make it happen I'd rather take the winners.