In a nutshell, I recall reading somewhere that this was done to keep the number of Jews down in the universities (rampant anti semitism at the time). Apparently there were too many Jews for the admissions committees comfort at the time (the 40s maybe?). The idea was that Jews would easily be admitted using academic measures. But if other measures were introduced, admissions committees could use the extracurriculars as a way of excluding people. Am I the only one who has heard this?