I think that in many cases these specialty "tiny houses" are work arounds for zoning laws of putting "trailers" or RVs on a piece of property. Yes, they may be "mobile" to get them on site, but in reality they are not road worthy. In addition, you will notice some do not even have bathrooms, so I think in those cases zoning looks at them as "sheds", but of course the owner has to put it where they can use the facilities of the main house.
What we find humorous, is that while some of the shows focus on specially built units that are very space efficient like an RV (although most still seem un-livable) others have people looking at other small buildings that may be "livable" for short periods of time (like a "cabin"), but are so inefficient in space manage to you could never really live in them long term......
2015 Tiffin Allegro 31SA, 24k chassis
2015 Jeep Cherokee Trailhawk