> There isn’t a single end feature that you can deliver in Rust but not C.

There are! Namely, when it’s open source with volunteer-ish developers, who cannot be arsed to not use Rust, as it’s simply that much more pleasant to be spending your time with.

So in some sense, it’s either done in Rust because the implementers want to for one reason or another, or just not at all, as no one can be forced.