Ubuntu has personal PPAs that are easy to setup - but Ubuntu has a good system to get everything into mainline (mostly because Debian has nearly everything and they ship Debian) and so they are rarely used. Arch has vastly less official packages and so there are a lot of niches where you have to use a AUR.

I don't think the issue is Arch is to strict though. I think the issue is Arch isn't good at helping people getting things that should be official to official. Publishing a AUR is easy, getting something from an AUR to official is hard and most people give up - often without trying.