Rewards are low in games where successful outcomes are of high likelihood. Getting an A in a Gender Studies class (which has a likelihood of 92% at Yale) is succeeding in principle, but failing at doing something worth doing.
92% of grades in Women's, Gender, and Sexuality Studies classes at Yale are A or A-, vs 55% in Mathematics. The math majors must just not be as smart. (Table via @sfmcguire79.)