The one thing I dislike about teaching is dealing with the students who think their grades are lower than they deserve. And it's always a matter of "deserve". So far I've only had one student who came out with a full sense of entitlement, "I don't get D's", but I've had every reason to want to track down whomever coined the phrase "A for effort" and give them a stern talking-to.
I made the mistake of returning final papers on the last day of class, not at the final exam. I wanted to remove a bit of uncertainty from their lives, and let them determine just how much studying they would need to do to get the grade they wanted. Unfortunately, this also gave them time to complain to me about their grades. One student emailed me, explaining that "I do not believe the grade I got in lab reflects how much effort I put into the labs". Another student asked to meet with me because she had some questions about grading, spent 15 minutes listening to me explain her grade, and then asked "But what about all the effort I put into this?". It's all I can do not to bang my head on my desk.
I can see where students' expected relationship between efforts and grades comes from. I don't even entirely blame some cultural movement that's deluding students into believe that working hard is all that matters. Generally speaking, when you put more effort into something, you get a better product, so effort and grades are usually correlated. However. Better does not necessarily mean A-quality. It doesn't matter if a student put 10 hours into a paper; if that paper doesn't meet the standards I laid out for an A, then it doesn't get an A. If it doesn't meet the basic requirements I put into the assignment, it doesn't even get a C.
Dealing with students in these situations is challenging. It requires a great deal of self-control. I do not respond to emails by saying that the grade doesn't reflect your effort because you turned in your final paper late and got hit with that late penalty, that I've already made two exceptions for you and won't make a third, and that I don't care whether you can get an A in the class. I do respond to questions about effort with "I don't care how much effort you put into it", just because the question frustrates me. I carefully explain that grades are based on the assignment that is turned in, and start explaining, again, how that grade was determined.
This has to be the best argument against assigning papers. Even when you think the reading and the grading are fun, the subjective nature of grading invites students to convince you to change the grade.