Typically Rust programs are distributed in pre-compiled form so you don't have to have a Rust compiler installed. I'm not sure why this project ships source code currently, but it could probably ship binaries too.
I get most of my Rust binaries through cargo when on Ubuntu, except in a few cases when I really want rg (still not available in Ubuntu 18.04) but don’t want to waste 25% storage on the Rust tool chain.