I would guess some of it is about the level of competition and the realization of ones talent level.
STEM…STEM…STEM… it’s been non-stop for years. In high school, good students have options for AP and honors math and science classes that drive weighted GPA and class rank. In our school, non-STEM kids are at a severe disadvantage for weighted GPA (far fewer classes with bonus GPA points).
Then they get to college, and are confronted with 2 realities… 1) this stuff is really hard, and 2) these other kids are really smart. After a semester or two, non-STEM majors look like they have a lot more fun than the folks in my classes.
As for Pass/Fail mentioned in the article, I think most schools use the letter grade for your major in calculating GPA.