Rust is a tool that allows one to build cars for humans to drive, in order to avoid certain accidents. If you try to put your dog in the driver’s seat of a Rust-powered car, Rust will stop you and ask you to produce proof that the dog is a qualified human driver.
The world is a pretty big place, so of course there are people who sometimes put their dog in the driver’s seat. Sometimes by accident, sometimes out of necessity, and sometimes because they think it’s mighty fun. Since Rust is strict about who or what gets to drive the car, these people build their cars using other languages.
Some Rust-heads, however, are pretty adamant that cars are to be driven by qualified humans only, and therefore keep nagging everyone about how all cars should be built with Rust.