Zig is “c”, but modern and safe.
Zig is safer than C, but not on a level that is comparable to Rust, so it lacks its biggest selling point. Unfortunately just being a more modern language is not enough to sell it.
So imagine if trying to fit in a C-like cousin failed
C++ was not added to Linux because Linus Torvalds thought it was an horrible language, not because it was not possible to integrate in the kernel.
Most of those companies actually contribute to the kernel or to foundational software used on servers, but few contribute to the userspace for desktop consumers on the level that Valve does.