The Kernel coding style wasn't written a week ago. The first I read it, more than a decade ago, the GNU coding standards did matter and I remember feeling quite hurt by that (in a good way, since I don't think anybody took it that seriously).

Matter of fact, the GNU coding standards still matter (to a certain extent) to many of us, and you would be thankful that they did, since it's the basis that provides consistency among GNU (and non GNU) command line apps, for example.

The GNU coding standards is an extensive document which doesn't only talk about how to write C code, but also how to talks about how to design software consistent with the GNU principles (command line user interfaces, options, stdin/stdout behaviour, etc).

Personally I take the kernel coding style as a whole different thing. It's a short guide on how to write consistent code for the linux kernel. And full of good opinionated choices in my opinion. Its scope is very different from that of the GNU coding standards (which, I'd say, is focused towards writing userland programs which the user will interact with).

Also, remember that GNU wanted (wants?) to create an OS, not just a kernel, so I guess we can read their guidelines as something similar to Apple's human interface guidelines for devs :)