Just thinking about this from the perspective of law schools, the only reason that I went to Duke for law school was because of it's rank as a T14.
I basically paid for a title of nobility, for lack of a better phrase. Granted, it's a lesser title (and I'm still kind of ashamed since it isn't Harvard or Yale), but I knew I was buying a title and wasn't really trying to get an education.
People get into top law schools largely based on college GPA and LSAT scores. If the legal training at top law schools is not better than at other schools, why don't top law firms recruit at less prestigious law schools, filtering for students with high GPAs and LSAT scores?