<p>At least in the math department almost all grad students have to teach/TA almost every term, and almost all of them go on to teaching positions, more often than not at non-Ph.D granting schools, after graduating, so their future employment prospects certainly do depend on teaching skills, so they tend to take teaching reviews seriously.</p>
<p>On another note, I’ve taken several classes where the professor did not provide the grader with solutions to problem sets, and the grader did not know the solutions- at office hours the grader said that (s)he would see if any of the students turn in solutions that seem correct- if so they would grade the problem accordingly, if not give full credit for anything “reasonable”. Classmates are often a better source of help than graders/TA’s who know only a little more than you (they often took a less hardcore version of the corresponding course years earlier as undergrads at NOTCALTECH, so its not unreasonable to expect someone in the class to understand the subject matter better than them) and have better things to do with their time than solving YOUR problem sets. Nevertheless the TA’s are generally nice people and want to help you to the best of their (somewhat limited) ability…</p>