1. Reading the cases just reinforces the doctrine for me. Maybe I learn differently, but it is where the law comes from and I like to know the "why" of it. Why did a judge or jury decide this way on this case, but another court decided differently on another case, etc. The decisions reinforce the black letter law and, for me, makes it easier to apply when given a scenario. I remember the cases, which is required for our torts class on an exam. She wants us to analyze and compare a case we read to the scenario given in some detail. If you don't have to do that, then you probably could spend your time doing other things. Again, a student should be prepared for what is expected by the professor and I'm sure you agree with that.
2. You are probably correct that one will get extra points for things not mentioned in class. One of my professors says we don't have to use policy arguments in our answers, but based on many 2L's experience at my school, it will get you additional points. So definitely add it if you have the time.
Again, I really won't know how I'm doing til I get my grades. But for now, I really don't mind putting the time in. It's not overbearing or killing me or depriving me of a social life. It's all good right now.
First: What benefit do you get from reading the cases? (I'm not implying there isn't any)
Second: Yes, in most cases you absolutely will get extra points for mentioning things not covered in class. Professors pretend that their test grading is so accurate and particular. They claim that they will only give points for things covered in class. However, I got plenty of points for public policy and logical arguments that weren't covered in class. I brought my professional experience into finals all the time and got a lot of points. Professors also warned against using commercial supplements because they would include information that wasn't covered in class. I relied on these all the time and got points because the law was correct. Law school grading is about organization, black letter laws, exceptions, good logic and application, and then interesting points that the teacher likes. I took a risk one time and went off on how the fact pattern in a final would never happen, and it wouldn't be in the business' best interest to sue. I said if they did sue, the issues and likely outcome would be _____, but the first question is whether a law suit was even a good idea. I got the book award in that class even though the teacher had professed that he would not give points for anything that wasn't covered in class.
Finally, I don't think anyone is saying you shouldn't read the cases. However, don't think that it's the most effective method just because that's what you are "supposed" to do. For every minute you spend reading the book you could be doing something else.