alt Hacker NewsNot for everything. For code you own, yes this is often the case. For the majority of the layers you still rely on documentation. Take the project you mention going straight to source, did you follow this thread all the way down through each compiler involved in building the project? Of course not.
My understanding is that "literate programming" doesn't say "you should document the public API". It says "you should document the implementation details, because code is hard to understand".
My opinion is that if whoever is interested in reading the implementation details cannot understand it, either the code is bad or they need to improve themselves. Most of the time at least. But I hear a lot of "I am very smart, so if I don't understand it without any effort, it means it's too complicated".