It's not more common because the US has a metric fuck ton of land and people want to raise families one day. The wiki entry even says that this is traditionally for the homeless. I instantly got Army barrack vibes from this, but at least that's usually for the early bootcamp days for the first few years, not an entire lifestyle choice.

I only really see it justified for single young people, but even then $700 for this is insulting (even for a place like SF) unless I'm missing something. Why not just rent a communal house at that point?