We don't need the advisor to tell us if a student's work is of high quality. In fact, the advisor, being a participant in the research, is not qualified to evaluate it at all. Objectivity is a sine qua non of scientific discourse and the advisor doesn't have it. Clearly, this evaluation should be carried out by faculty members who are as far removed as possible from the research group while still being capable of understanding the work. Let's face it, what we do now is as stupid as having someone's close colleagues referee a journal submission.
Advisors have no business evaluating their own students.
In the long run, most advisors would undoubtedly appreciate being able to work with talented students without the specter of the Recommendation haunting everyone. If anyone tells me that advisors need the Recommendation as a cudgel to get their students to work hard, I'm going to reach for my gun. Figuratively, of course. Check this box only if you would also like this submission to be considered for publication as a letter to the editor in the printed edition Chronicle. Be sure to include your name and affiliation.