It takes a while. At Google at least, new systems in android are required to be built in rust and there are major efforts to rewrite significant systems. But it

It takes a while. At Google at least, new systems in android are required to be built in rust and there are major efforts to rewrite significant systems. But it takes time and rewrites are dangerous in other ways. And you need all the tooling to handle everything else an engineer does beyond simply writing code. From where I sit, it also feels like the industry has really only coalesced around "the only real solution is safer languages" in the last 2-3 years. "Rewrite it in swift/rust" was way more controversial in 2019. So hopefully we'll see significant progress in the next several years.