Came here to say this. Archinstall rocks.

Regarding why Arch doesn't "invest" in a graphical installer, it's worth mentioning that Arch's installation image has a different design philosophy than most installation media.

The image is a fully functional arch environment that copies the entirety of its contents to RAM on boot, giving you special installation opportunities such as the ability to install Arch to the same flash drive that booted the installer. Having no graphical dependencies lets this image remain small enough to pull this off, as well as allowing for fully remote installations over SSH out of the box, since archinstall is a TUI.

I don't believe there are any serious technical obstacles to providing a graphical installer in something like an initramfs environment. Many distros do provide graphical installation mechanisms using PXE, which loads the kernel and installer-initramfs over the network (and is similar in the sense that it won't touch local storage unless you tell it to)

I don't have a way to quickly around to check, but I thought the arch install media used squashfs? In which case I wouldn't have thought it was safe to blow away the backing store.