What you're describing may be part of the issue, I can't argue with that, but come on. There are lots of reasons that people might cheat in classes that they enjoy or that they recognize is useful. I've been lucky enough to have very little cheating in my classes, but it's easy enough to imagine.

Let's say Johnny wants to be a doctor more than anything in the world. He knows that he needs two semesters of Organic Chemistry on his transcript to get in to med school, and that if his grades aren't top notch he won't be able to compete. Johnny likes his Chem prof (and the grading is fair), but he's only managing B-'s on his exams. He sees his dream fading away. Sure, he could say, "Huh. I guess I'm not cut out to be a doctor." But don't you think some students out there would consider cheating under those circumstances?

Or maybe Johnny consciously chose to go to a college that has a strong culture of giving students a "well-rounded" education (by whatever internal definition) and insists that students take a wide variety of classes from different disciplines. That's not Johnny's cup of tea: he just wants a computing degree. He could easily have chosen a different school, but he didn't. Now he just wants to focus on his CS classes, so when he's stuck with a course in English or History he decides to cheat so he doesn't have to think about it. Do you really want to say that's the teacher's fault?