At a certain point, your resume should speak for itself. The fact that experienced engineers with impressive resumes are put through these types of interviews is insulting and frustrating to the interviewees. Succeeding at these whiteboard questions requires weeks of preparation. You need to practice, practice, practice. After enough practice, you are pretty likely to pass. So ultimately, it is more of a test of "how…
Of course, the irony is that for vast majority of the people they hire, most of the work they do will be building and not much algorithms work. So then what will happen is either you have people who are great at building things and force them to suffer through the interviews or you have people who are great at algorithms but not that interested in programming.
Of course, you might also have people who are great at both, but I wonder how many of them there are..