The Problem with Writing a Problem Novel

Problem novels have a lousy reputation, especially amongst adults. Which begs a few questions for which I, in my delusions of grandeurs(DoG), will answer. (See the trick here is that I pose questions that I know the answer to. Pay no attention to man behind the curtain.)

First, what are problem novels? In YA, they're novels in which the characters of the novel try to cope with issues like rape, domestic violence, homelessness, alcoholism etc.

Why are they so seemingly unpopular?...