Why c89? Why not c99 or c11?

Honestly curious about the decision to stick with c89. I understand that c99 had some flaws that prevented certain projects from adopting (Eg Linux kernel), but c11 has definitely fixed a bunch of stuff and provides nicer facilities for variable scoping to help remove bugs (eg Linux kernel allows c11). Plus, more and more people are getting involved with C in a post c99/c11 world. So further development assistance would feel more natural if we could push for a newer version.

What is the reason that nuclear mandates c89?what is the ethos behind sticking with this?