C has the benefit that it's as close as you can get to a WYSIWYG language. There's no VM or garbage handler running behind your back doing god-knows-what at the most inopportune time. You can look at the code and know exactly what instructions it's going to execute, every time.

(Yes the compiler can do some trickery at certain optimization levels but even then, you're able to look at the generated assembly very easily and verify the output you expect to see).

I'm a little surprised they aren't running their own OS with a custom scheduler; I guess the odds of that being bug free vs the odds of running into a Linux bug make it a losing proposition.