Using Rust for writing shaders may sound appealing, but that puts a language that is slow to compile into a domain where fast iteration times are crucial. Most shaders can be compiled in milliseconds and e.g. graphical authoring tools rely on this.

They see specific advantages here that would outweigh that negative. It's not my space (I play games, but know next to nothing about graphics programming), but there's at least one argument in the other direction.