[ihaveajob]

When I was a TA in grad school, I noticed the same. Early on I thought some BS answers were at least kind of funny, and I gave them the benefit of the doubt, maybe giving more attention to the parts that were correct. After I saw similar answers later on, the novelty wore off and I was probably less amused, so the inclination to be lenient disappeared. Sometimes I went back to previous decisions if I remembered them, to be fair, but I don't think I always remembered since the volume could be high (grading 80 exams in a row is TEDIOUS).