Agree the markets are small however your analysis is focused on rational profit driven applications. Consumers desire to own toys like RVs, boats and personal aircraft that are mostly parked might be a significant, even if small market.
One more small but not insignificant market might be wheelchairs. Hovercraft for the immobile for trips to the store, to the bathroom. The main advantage possibly being no obstacles like stairs, mud, sandy paths, home clutter.