A big part of why nix documentation is sub par. The essential tomes of nix - the nix manual, the nixos manual, the nixos options, the nixpkgs manual - each of these documents is just one long page.
They are the digital equivalent of scrolls, rather than books (codices?).
Rather than having a page number (or page link), one must unroll the scroll to the point of interest. One cannot simply flip between two points of interest. One cannot have bookmarks, or refer to page numbers. Ctrl-F is helpful, sure, but not great.
For instance, I was just looking for the documentation of the systemd.services. options. Its near the end of the colossally long scroll known as the Nixos Options Appendix. Ctrl-F on systemctl.services will get one million hits on all the myriad services nixos offers before you finally get to the relevant section. And if you do find that section (with single pixel movements of the scroll bar) and then ctrl-f, woe betide you, you're now at the top of the document and your place is lost!
Having everything in a single file is not really a problem.
Having extremely outdated info on topics like below is a major issue though.
Huh?
Page 1