“Despite its generally fast-moving nature, the kernel project relies on a number of old tools.”
The Linux kernel has been written in C89, a standard older than the kernel itself. What finally forced the change wasn’t style. It was a bug class in the linked-list macros. C89 can’t declare the iterator inside the loop, so it leaks out where code can misuse it. Thirty years of “if it ain’t broke” ended when it broke.