Most faculty does not want to grade anything. I've TA'ed 6 courses, the professor just showed up for lectures and reused last year's exams/homeworks. Students had the solutions, >70% of the class copied them exactly. The prof didn't care. And TA's were handling most complaints about the grades. This was common for majority of undergrad level classes I took (a different UC campus).
Also, it was my job as a TA to explain the material during my TA sections (which were basically lectures, only with more questions and more examples, and I used a blackboard while the prof just read PP slides).
Even though the above was the norm, there were a few great professors who cared, and taught very well.