See the [Arch Way](https://wiki.archlinux.org/index.php/The_Arch_Way), notably #1. Having a barebones system installed allows you to shape it any way you want (LFS style, without the hassle of bootstrapping and lack of package management), and sticking with as much vanilla packages as possible allows you to just use upstream doc, and makes bug hunting easier to report upstream too.

Ubuntu is the antithesis of that (no judgement here, I am fairly marvelled at the "pop the CD in and it just works" result of Ubuntu).