It's an understandable rule, and you can definitely just download the binary from alire.ada.dev and add it to $PATH but with such a harsh stigma around how difficult it is to get the toolchain set up, GetAda follows the precedent of Rust, where you can grab the toolchain via "curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh" (thanks to Rustup).

It was received positively at the time:

Show HN: Getada: rustup-like installer for Ada's toolchain/package manager 194 points | 115 comments: https://news.ycombinator.com/item?id=40132373