There are some things that both a book index and even full text search cannot solve. For example, if the teacher asks why in the Pride and Prejudice does Elizabeth lose temper on Mr. Darcy?, those smart-on-the-surface solutions can't take you anywhere.
On the other hand my friend from the other school can easily tell me to go to page number 432 on the book to find the exact answer because labeled pagination has reference accessibility [1] along with random access.