It isn't common but it definitely happens in some parts of the US.

There are no taxes to pay if you aren't earning anything. It is legal, if inadvisable, to raise children this way in much of the US. There is a "live and let live" ethos around it, especially in the western US. The true nomads are probably most common in the mountain West of the US in my experience. While the rule is two weeks in one location, in many remote areas there is no enforcement and no one really cares. They sometimes have mutually beneficial arrangements with ranchers in the area. These groups tend to be relatively small.

Alaska is famously popular for groups of families disappearing into the remote wilderness to create villages far from modern civilization. It is broadly tolerated there. Often many years will pass between sightings of people that disappeared into the wilderness.

I always wondered what a high-resolution satellite survey of the Inside Passage of Alaska and the north coast of British Columbia would find in that vast and impenetrable wilderness. Anecdotally there should be dozens of villages hidden in there that have been operating for decades.