[littlestymaar]

Why wouldn't they do exactly that if they decided to publish binary crates…

Nobody does that right now because there's no need for that, but it doesn't mean that it's impossible in any way.

Stable ABI is a massive commitment that has long lasting implications, but you don't need that to be able to have binary dependencies.

[zozbot234]

You can have binary dependencies with a stable ABI; they're called C-compatible shared libs, provided by your system package manager. And Cargo can host *-sys packages that define Rust bindings to these shared libs. Yes, you give up on memory safety across modules, but that's what things like the WASM Components proposals are for. It's a whole other issue that has very little to do with ensuring safety within a single build.