Many people know and like C. Many companies have access to plenty of C talent, but no Rust talent.
These are two great reasons to try Fil-C instead of Rust.
It seems that many Rustaceans think in terms of their own small community and don’t really have a feel for how massive the C (or C++) universe is and how many different motivations exist for using the language.
I agree, but the converse is also true and is where the value of this DARPA grant lies:
There's a lot of legacy C code that people want to expand on today, but they can't because the existing program is in C and they don't want to write more potentially unsafe C code or add onto an already iffy system.
If we can rewrite in Rust, we can get safety, which is cool but not the main draw. The main draw, I think, is you now have a rust codebase, and you can continue on with that.
These are two great reasons to try Fil-C instead of Rust. It seems that many Rustaceans think in terms of their own small community and don’t really have a feel for how massive the C (or C++) universe is and how many different motivations exist for using the language.