The use case isn't that narrow though. Just the flet project has 12.5k GH stars (which I would say represents significant adoption), and I'll wager there are other projects out there running in random environments that have Python support but bringing in Rust will be a serious pain. It's degrading the ecosystem IMO. The only other language I'm aware of that has significant library wrapping is Fortran, and those libraries have on par or better alternatives in C as well as are now essentially legacy.