There are two reasons that I don't think this is the same issue as putting a copyright notice on every single page. 1. Each page of a book is not meaningful in

There are two reasons that I don't think this is the same issue as putting a copyright notice on every single page. 1. Each page of a book is not meaningful in of itself in the same way that a particular function in a file is meaningful in of itself. So, there's no real worry that the text will be moved to another place without the appropriate notice being copied along with it (citations and quotations are usually under fair use, and citing a work is usually the only thing you need to do if you copy part of a work). 2. Pages in a book are not like files. If you were talking about pamphlets, the analogy would be more clear. It is not expected that people will tear out pages from a book and then stick them into a new book. It is also not expected that people will only be given a single chapter from a book rather than the whole book. If any of those cases were considered "normal use" of the book, then I would definitely expect people to put a copyright notice on every page. In addition, it isn't common for people to apply different licenses to different pages of the same book. Usually the license and copyright are the same for the entire book. Not to mention that IMO it is aesthetically pleasing to have a nice header in each file, and it doesn't have any ambiguity when you read the code of a project what license applies to which file. Also, it's how all GNU projects do it and I trust their lawyers and opinion on how to correctly display licensing information. It also mentions that this is the recommended way of displaying the license in the actual license text itself. So there's that.