I see "Arch btw" crowd as the new gentoo except even easier so more people actually do it.
You see, Arch is a highly exclusive club of high iq individuals who can read a wiki and use a "rolling release" distro, meaning they get bleeding edge updates only! And of course when things break they're high iq so can fix them but things seldom break. especially when you almost exclusively use your computer for browsing the internet
Really though I think it's mostly just people trying to feel smart and/or unique, especially before it got meme'd to death and everyone was doing it. You'd be quite the badass if your neofetch shows you run arch while showing off your tiling window manager anime desktop minimal rice.
The actual utility from Arch is the AUR but you don't need to use Arch itself to get that benefit.