It depends upon whom you ask, as reported by Beckie Supiano in the Chronicle of Higher Education.
The issue was at the heart of a recent debate over whether to change the grading system at Eastern Washington University. EWU had long awarded course grades on a 4.0 system, in which grades are given to the tenths decimal place, offering many more options for professors than the more conventional letter system. Instead of awarding an A or an A-minus, for instance, professors might give a 3.7, 3.8, 3.9, or 4.0.
The debate revealed that professors in STEM fields wanted more precision, while those in other disciplines preferred to exercise more personal judgment. Please read the article for details.
The STEM professors have a point (no pun intended). They wish to subtract incremental points for “small mistakes,” as they put it. Let’s assume that your school doesn’t even allow for minuses and plusses. That’s a lot of variety within, say, a B. On the other hand, with many subjects minute quantification would be unreasonable to expect, especially in the liberal arts, fine arts, and humanities.
An aspect of this discussion unmentioned in the article involves what happens after grades are awarded. The more data points allowed in the grading system, the more points of contention you will have. Schools generally allow an appeals process on grades, where students can make their case. While most students are unlikely to contest a 3.4 versus a 3.5, you can see the potential.
Grading the written work of students presents a host of problems. If you grade an essay or paper on how well the student sticks to the topic and carries the narrative smoothly and precisely, how do you quantify that? Forget about grammar-checker software, especially with a program that starts with W, by a company that starts with M.
The desire for quantification is one reason why multiple-choice exams are preferred by many students and faculty. It’s not that teachers don’t want to read papers, it’s that justifying a score becomes increasingly difficult, especially in the student-as-customer era in which we live.