This is a very good question. Unix/C came from the glorious "system building" era. They took responsibility for building and documenting "the whole stack" - from assembly to signals to troff. Wirth's Oberon OS/language were codesigned in the same fashion. Smalltalk/V took over a PC.

Ceylon seems like a very nicely designed language (and I don't mean syntax). I would love to see a LLVM back end and the requisite docs for low level system hacking.