With interpreted languages with language-specific package managers, you have to:
1) Install the language
1a) Possibly have to install a language version manager (rbenv, pyenv, etc)
2) Install the language's package manager
3) Install the CLI utility via the language's package manager
Here's the order I think CLI maintainers should strive to making their utilities available:
1) Install via OS package manager
2) Install via prebuilt release with OS-specific package, from hosting site (GitHub, etc).
3) Install from source
4) Install via language-specific package manager
5) Install via curl | sh :)