Arch is a DIY distro, so I understand why they promote the manual installation, it allows the user to better understand the inner workings of the OS and in case of problems the user should have a basic understanding on how to troubleshoot the system to get it back in a working state.
I did personally start using Linux a couple years ago with Manjaro, then when they decided to maintain their version of Mesa with the proprietary codecs disabled I jumped ship and installed EOS. In the meantime I installed Arch inside a VM just to tinker with it and I guess I learned some basic, but useful informations.
I also believe that an OS is just a tool, not a cult, but for distros like Arch, Gentoo and even Debian I’d argue that having a better understanding of how to partition a drive, how to restore a bootloader in case it breaks (thanks GRUB for the continuous lessons /s), how SystemD operates and stuff like that can really help you out.