Why do universities place a weight on GRE/TOEFL scores? This is one question that has been bugging me for a long time now. Why do universities consider GRE/TOEFL scores at all? Perhaps it is fine for master's degrees, where there will be an enormous number of applicants whose language abilities cannot be otherwise established. But what is the necessity for a PhD degree? Why not zero in on a small group of candidates based on their profiles and then conduct a Skype interview? That way the professor gets to know both the verbal and the research potential of the student. Why isn't this the case for PhD admissions?
GRE/TOEFL scores are used in a number of different ways (some of which are alluded to above)


GRE scores are sometimes used as a university-level filter (if your GRE score is &lt; X, then you'll need a strong support letter from your department to get admitted)
TOEFL scores are used as a filter for giving people TA funding (if your TOEFL score is too low, you can't be assigned to be a TA, and if it's lower, you can't even get RA funding)
More informally, the GRE/TOEFL scores are used as a "do you even care' filter: for a CS program, a quantitative score less than 600 might be considered to be a warning that the candidate doesn't even care enough to prep for it. 


But for Ph.D programs, the GRE/TOEFL are either used as a high-bar disqualification filters to prune applications (in top schools), or as low-bar disqualification filters to prune the non-serious applications.