求一个句子的含义

TheAssembly

LSAT逻辑一道，没什么复杂词汇

Some teachers claim that students would not learn curricular content without the incentive of grades. But students with intense interest in the material would learn it without this incentive, while the behavior of students lacking all interests in the material is unaffected by such an incentive. The incentive of grades, therefore, serves no essential academic purpose.



问：serves no essential academic purpose.是什么含义？