The regular user only installs software others have packaged.
I end up packaging software sometimes (maintain a few AUR packages) but my main use-case is being able to modify the packaging myself for private use, generally to apply custom patches or alter compiler flags etc.
Being able to do all of this easily without ending up with a pile of goop everywhere from `git clone thing && cd thing && make && sudo make install` is nice.
Honestly, I think AUR is one of the best things to ever come out of Linux, because it's not just a repository.
> plus PPAs in the form of other OBS repositories if you really need them, but you almost certainly don't
This is extremely presumptive and wrong. I find it very frustrating that any issues with these official repos is dismissed as "oh but you don't need extra PPAs ever". My guy, yes, I do. It happens way too often and it's very frustrating when it does, because the options for handling it in non-Arch based distros are completely insufficient and terrible.
But then again, what do I expect. Any complaints about Linux are pretty much always dismissed out of hand.
I actually prefer using Windows because Windows users generally aren't such arrogant pricks when there are issues.
back when I was using arch I wrote pkgbuilds instead of configure/make/installing to my home folder. kept my ./local/(bin|lib|share) clean and meant I could update it easier or uninstall it with pacman.
As to runnning random build scripts, well I already do that anyway. Any software that isn't provided by my package manager requires me to run random build scripts from random people. I sure as hell am not reading through every line of code in say... trealla prolog before make-ing it.
This is exactly what a tech savvy user would do.