Via @mitsuhiko elsewhere:
Pi wouldn’t make any sense in rust or go. Extensibility is key to it. That leaves ruby, python, js, php for the most part unless you want to ship an interpreter. None of those languages have any benefit over node.
This is the big decision when building a CLI app: is it going to get big and have an ecosystem? If yes, better use JS/TS because plugins run in-process. Less fun in Go and Rust.