Any reason to use Scala native when Rust exists?
The maturity of the eco-system.
Not having to deal with the borrow checker.
In any case, I would say in such cases OCaml and Haskell are also good candidates.
Scala, Haskell, OCaml are garbage collected languages. This makes them easier to use, but some problems are out of reach.
Embedded development, kernels, native apps requiring performance without frames dropped, real-time systems actually, including consumer stuff like decoding video, these have been the domain of C/C++.
Of course, there are projects out there using these languages, pushing the boundaries, like MirageOS (https://mirage.io/) which is built with OCaml. But those are like the exceptions confirming the rule.
The ongoing NLL work proves ergonomics are still not there, and it doesn't cover all scenarios like internal references as done typically for callbacks in GUI widgets.
It will surely improve, and the best thing for polyglot developers is that we can easily pick the best tool for the job.
I feel like if anything, Rust sounds more powerful to me, greater performance, control over memory, low level unsafe access, etc.