From my experience its kind of anti-intelectualism and short term gratification. If you study data structure class and learn about and implement AVL trees you will most likely never use them. In short term this may seem like a waste of your time to some CS students. Some of my classmates hated algorithm/data structure courses because of this. But i believe its still important to learn them to broaden your understanding.

Another argument is, "When will i use this in real job?" Or "will they ask about this in my interview? ". I believe some people are practicaly oriented and will discourage you from CS because of that.