Questions about Arch Linux and the Arch User Repository (AUR)

I have a few questions, thoughts and concerns about Arch Linux and specifically the AUR (Arch User Repository). As far as I understand it’s possible to build packages by your own on practically every Linux distribution. Only the sources of the package you want to build and the suitable build tools for the distro are necessary. Because this is not very convenient for the average user there are prebuild packages which can be easily be installed. These packages are usually provided by the developers of a package (software). The developers offer different versions of their packages for different Linux distributions. Packages for Debian, Ubuntu etc. are always available, but not for Arch Linux. This is where the AUR (Arch User Repository) comes in place. I understand it as a platform where members of the community can upload self prebuild packages. Other members can easily install those packages, like the ones the developer offer for other distributions.

Why is Arch so popular although a lot of prebuild packages are not provided by the developers of the package? Why are Arch users so proud of the AUR? Why do they understand it as something good? Like an advantage over other distributions?
In my opinion the AUR is only necessary because so much official packages are missing.
When I install a package from the AUR I completely rely on the maintainer of the AUR package. I don’t even know if the package which is provided by the maintainer really is build from the original sources. I have to trust the maintainer 100%. If I would use another distribution I could use official packages. And I assume that the developers of a package will always provide the newest version of the prebuilt package and will maintain it. But I can not be sure that a voluntary AUR maintainer will always keep the package up to date.

So what’s the point about Arch and about the AUR? Is anything I wrote wrong? Am I missing anything? I hope I made myself clear. Maybe someone could lighten things up a little bit. Thank you.