Re: I wonder why?
Linus' potty mouth notwithstanding, let's not forget that some of this shit is hard - my last tussle with the kernel was way back in the 2.mumble days where I had to write a couple of drivers for some hardware in my lab - my C chops were a lot better back then but even so, hacking on the kernel was not for the faint of heart (one bit of hardware was sorta-kinda supported, which made life a bit easier, but the other wasn't so I had to work from datasheets and whatnot and write everything from scratch) - still gives me nightmares.
You want documentation? Well, there's the code itself ... other than that, good luck!
I probably wouldn't even know where to start now.
There's also the 'some of this stuff is boring' aspect - whilst you'll probably have no shortage of people queuing up to work on the latest shiny shiny or the $ARCHITECTURE_DU_JOUR, there's no escaping the fact that the 'boring' stuff in the kernel will need occasional care and feeding as well, and that's not as sexy by half and people will be less inclined to do anything once the current maintainers have moved on[*]
[*] - I'm one of those developers who actually enjoys working on the 'boring' stuff. It's a dirty job, but someone's gotta do it ...