Majority opinion seems to hold that teaching composition MEANS teaching the rhetorical modes; that certainly is what everybody did when I was a graduate student in the early 1980s. But I have read entirely too many place descriptions about teenage bedrooms, process essays about how to change a tire, narratives about car accidents (or, for the more nostalgic, high school proms and graduation ceremonies), contrasts of high school vs college, definitions of success, and research papers about abortion, the disease of the month, or the death penalty.
I'm not sure to what degree (if any) there's a causal relationship between teaching rhetorical modes and students selecting such deadly dull topics. Or is the problem that students, for the most part, seem to have difficulty handling personal topics (either because they haven't acquired the necessary perspective or they can't summon up the telling details of their lives)? The old form vs content debate.