Stephen Leacock explained, a century ago, about book indexes. His essay begins:
“Readers of books, I mean worthwhile readers, like those who read this volume, will understand how many difficulties centre round the making of an Index. Whether to have an Index at all? Whether to make it a great big one or just a cute little Index on one page? Whether to have only proper names or let it take in ideas – and so on. In short, the thing reaches dimensions that may raise it to the rank of being called the Index Problem, if nothing is done about it. Of course one has to have an Index. Authors themselves would prefer not to have any. Having none would save trouble, and compel reviewers to read the whole book instead of just the Index….”
BONUS (somewhat related). The 2007 Ig Nobel Prize for literature was awarded to Glenda Browne of Blaxland, Blue Mountains, Australia, for her study of the word “the” — and of the many ways it causes problems for anyone who tries to put things into alphabetical order.
Browne’s report is: “The Definite Article: Acknowledging ‘The’ in Index Entries,” Glenda Browne, The Indexer, vol. 22, no. 3 April 2001, pp. 119-22.