Another point is ecosystem. Imagine you trained your whole team on Rust and got the entire codebase scrapped. Now you have to actually go and rewrite all your upstream dependencies. Each library, infra integration, algorithm, data structure, etc.
Then, you gotta hire new people when those leave, and the rust hiring ecosystem is also just not there yet.
I worked mostly in robotics. Literally everything is cpp. All the grad students know it. Ros is there setting the mental models for better or worse. The list goes on.
You have really strong points on hiring, but the notion that you need to rewrite all your dependencies pretty weak. Nearly every modern language includes facilities for writing findings and I do believe that there are Rust to C++ binding tools.
This is true in theory, but in practice is a nightmare.
YMMV, but even small bits of python, Go, or (yes) Rust that have crept into the robotics stacks at the various places I've worked have created problems for incoming new-hires, or for maintenance even for senior folks. Python less so than others, but python is challenging to deploy on vehicle, b/c of various hard and soft problems.
In particular, Rust interop with CPP is poor. Should I recompile all ros packages to allow me to call a few things in Rust? Not at this time.
imo the issue is that doing academic training in robotics means doing whatever your advisor tells you to do and playing the academic rat-race game OR working in industry churning out features as fast as possible to keep your company alive, which essentially means that you are not going to be able to spend any meaningful time learning how to do FFI in Rust or Python or whatever. I think that's the real reason robotics software is in the dark ages. But then again, I'm not in the field and this is an armchair take. So yeah.
Then, you gotta hire new people when those leave, and the rust hiring ecosystem is also just not there yet.
I worked mostly in robotics. Literally everything is cpp. All the grad students know it. Ros is there setting the mental models for better or worse. The list goes on.