The EPUB standard is a typical example of a standard that has been ruined by having too many cooks. It has too many features, with too many caveats trying to cover too many use cases. It ends up not covering many useful use cases, making the implementation of other useful use cases too hard and forcing any would be implementers to jump through three million microscopic hoops in order to "comply" with it. What a waste of electrons.
These kinds of standards are almost never implemented fully. They presumably exist for one reason only, to keep the standard writers from doing something even worse, like starting a world war.
