Questioning the practice

I got a letter from a kid the other day. After the opening paragraph, where he told me several reasons he liked my book, he wrote, "I have a question." This sentence was followed by 22 questions, ranging from "When did you get your first A+?" to "Are you rich?" I think the question I'm going to answer is, "Do you like getting letters?"

Okay -- I know there are lots of teachers out there. Maybe one of you can answer my questions. Why do these "write the author" assignments always involve...