Expediency might be one reason for cheating, but I'm not sure its the main reason. In fact, strangely, young people will sometimes go to greater lengths to cheat than to study for a test. Occasionally, this is due to boredom. Studies indicate that there is a high correlation between certain pedagogical practices and cheating behavior: lack of clarity in a lesson, perceived lack of relevance, and too few tests offered in a grading period are just a few examples. I've even wondered at times if cheating isn't some form of student protest against certain types of curricular or pedagogical factors. One mathematics teacher had an interesting insight into a student who had gone to elaborate lengths to program his calculator to outsmart his teacher.