When I was an undergrad, there was a certain course that was required for my degree. So the college held that course once every 4 semesters and just threw everyone into that one section.
What this meant was that the course would only be offered twice during the average student's time at the college, and depending on what other courses you needed and prerequisites, you might only be eligible to take it once.
And you had to take this course to graduate.
So one of my classmates decided, the only semester she was eligible to take the course, that she'd rather take an elective, in a completely different department, that was held at the same time as the required course. Because that's what college was all about--exploring things you'd never studied before. All her friends told her not to do this, her adviser told her not to do this.
Guess who was surprised to find out that she could graduate on time, because she had enough credits, just not with a degree in her area of study?