Because humor is funnier when you know it's true.
The trade
As a freshman engineering student many years ago, I experienced a year of intense academic challenges and of powerful worldly temptations. My version of wine, women, and song was beer, coeds, and poker. Dorm and frat parties helped my quest for the first two, and playing cards filled the time in-between.
In fact, almost everyone in my dorm enjoyed these pastimes. One fellow fun seeker, I’ll call him John, became such a good friend that we decided we would sign up as roommates for our sophomore year.
But as our freshman year was winding down, we found ourselves with different academic dilemmas. John was an English major who preferred poker to studying freshman calculus. As a result, he had failed a mid-term exam, and was in danger of failing the course if he didn’t pass his final. I, on the other hand, was so overwhelmed with engineering studies that I had no time to finish reading D.H. Lawrence’s "Women in Love," and therefore was unable to complete the final exam’s take-home essay in my freshman English course.
John came up with an idea. Since he had already read that novel, he would help me with my reading problem if I would help him study for his calculus exam. I agreed. And so I dutifully listened to the synopsis of the novel he provided, at least enough to be able to write some sort of essay. John tried to listen to my calculus teaching, but would quickly get bored and say we needed to take a break to shoot some hoops. I hoped that he picked enough from my lessons to get by.
Ultimately I turned in my paper, John took his exam, and we left school to spend the summer in our respective hometowns. When I got my essay grade in the mail, I couldn’t believe it. The professor gave me an “A!” Since we lived far apart, I wasn’t in touch with John over the summer, so I didn’t know how he did on his test, but figured he’d bring me up to speed when I saw him at school in the fall.