Your instructor is expected to do more than you might think. They are not only responsible for helping students master the course material, but also for mentoring students, guiding them through life challenges, attempting to prepare them for careers, trying to influence them to be more ethical and empathetic people, and trying to prepare them for the “real world.” So while you think an instructor is being arbitrary, they probably have their reasons. For example:
An instructor is picky about MLA or other citation guidelines.
You have to learn how to avoid plagiarism now because other places might not be so generous if they find you using others’ work and claiming it as your own. You don’t want to be expelled from a school, fired from a job, or forced to resign from a position because you were careless with your attributions. A future employer probably won’t care if you “didn’t mean it” or if it was an “accident.” They have a reputation to uphold and the integrity of their company is compromised if the public realizes they decided to overlook a plagiarist.
An instructor seems to obsess over minor details.
Employers have their pick when it comes to hiring. If they asked for a cover letter to include certain things and you decided you didn’t have time to include them, that employer just found an easy excuse to cut down on the resumes they have to read. Likewise, if you submit to a publication and don’t follow their submission guidelines, they may use this as a reason not to consider your work. The world is full of talented people and they’d rather work with a talented person who saves them time and energy by following directions. If you aren’t convinced, I was once told someone decided never to work with a person again because that person hadn’t double-spaced their text as instructed. Imagine what a loss it could be to have this happen to you, especially if the person is influential in their field.
An instructor gives out a lot boring worksheets or what seems to be “busy work.”
Your instructor may have realized that if she does not hand out a worksheet to go with the reading, no one will do the reading. Or maybe over the years she figured out that students only do work if it receives some sort of grade. Because the students did not perform the work of the course in the first place, now everyone has more work. But the instructor has to do whatever it takes to get students to do that work or the students risk leaving the class unprepared, assuming they pass in the first place. And your instructor is well aware that having to repeat a course often messes up the schedule of a student. If giving out a worksheet prevents someone from becoming a fifth-year student, then that’s what they will do.