We don't tend to write about disease in fiction - not just teen novels but all American novels - because it doesn't fit in with our idea of the heroic romantic epic. There is room only for sacrifice, heroism, war, politics and family struggle.
– John Green
Teenage readers also have a different relationship with the authors whose work they value than adult readers do. I loved Toni Morrison, but I don't have any desire to follow her on Twitter. I just want to read her books.