It's because it's bleeding edge, extremely well documented and extremely popular. Bleeding edge is exciting and you're gonna end up on the arch wiki anyway regardless of distro, so you may as well go to the source.
Do mind though it doesn't mean it's easy, like at all, and I fundamentally agree, there's a million better choices for first timers.
I am this exact case and it's getting better. A month ago I installed Arch on my Nvidia desktop and it had multiple problems: returning from sleep, really bad cursor lag hitches, video would freeze at random, applications would flicker, etc. Nowadays most of it is gone, unfortunately the really bad freezes after changing resolution on monitors are still there though