All I can figure is it's a way to skirt zoning laws. They certainly aren't practical from a portability perspective. They're heavy, not aerodynamic and I haven't seen in any episode where they give an consideration to weight distribution. So they're just tiny houses, so why put them on wheels?
They should visit these people after a year. Half of them probably murder each other and the other half probably set their tiny houses on fire and push them off a cliff.