AUR isn't a package repo. It's a collection of user-contributed PKGBUILD scripts, to make building packages from upstream source distributions more convenient. It's not meant to be treated like an official repo of binary packages.
> AUR isn't a package repo.
What does the 'R' in AUR stand for? Rutabaga?
That's a semantic detail based on the choice of build from source over binary distribution.
This is also a terrible way to run a package build system in this day and age as well, if you like. I feel exactly the same way about it, and when I wrote that I understood what it was, so I didn't need that helpful correction (I first used the FreeBSD ports system sometime around the turn of the millennia).