When one is doing a research project, the ease of finding citations is nigh paramount. It is helpful when all the works cited are in a handy list in the back of the book, so one can scan them rapidly. So why do some books only have footnotes?
The author already has all the information, because he put it in the footnotes. The formatting and typesetting are, nowadays, trivial. The amount of time I put in trawling through the footnotes, however, is not.