Scala is a strongly typed, very-well vetted, functional programming language in the JVM. It pretty much has everything going for it. It's even adopted by twitter.
Might as well ask why Scala didn't take over from C++.
Is it fair to say that the significance of those points are these?
no JVM: easier deployment
not garbage collected: less latency
zero-overhead abstraction: smaller in memory
You could say instead that Rust is a Scala-inspired systems language. Not just Scala, obviously, but by functional programming concepts like algebraic data types and type inference. Rust isn't even really a functional language itself; it's still an imperative language.
The list of complains grew big, but again: all in all, I think Scala was quite fine to work with.
Hard to respond to that as it is so general.
> It's even adopted by twitter.
And larger companies than Twitter use Rust (though to be fair not as extensively as Twitter uses Scala).
They're really not comparable. Rust is a lower-level language with no garbage collection (yet with guarantees about memory safety due to ownership rules). Scala runs on the JVM and has significantly more in the way of OOP (depending on how you use it obviously).
That said, I've found that my extensive Scala experience does come in handy when learning Rust as some features of the type system, pattern matching, threading failures through with ?, etc. These are things you won't have any familiarity with from Java, but do from Scala.
Scala is a disgusting mess compared to Rust in just about every way I can think of. Please for the love of everything good, consider at least Kotlin.