Given all the enthusiasm around Rust, why not SPARK 2012?

We all know that rust is great, and rust aficionados can't stop telling us about how great it is. One question I have as a European developer who has worked in both languages is, why not SPARK 2012? Ada is a much older language, and SPARK is a provable subset of it. If you value correctness, why not SPARK? It is provably correct, has not errors and has nice tooling and decades or real world experience and practice behind it.