Sorry, he pointed out cost, lack of storage and limited seating also so I wasn't sure what exactly you were trying to use motorcycles as the example for.
With that said Motorcycles and scooters aren't a good replacement for a car all year around in all places. I don't see people riding either when there is ice on the roads or when there is a few inches to a few feet of snow on the ground. They are fine for mid spring to mid fall in the north. However I would have to agree that none of them are practical for winter up north. Although as you pointed out that just puts them into the same usablity group as a motorcycle / scooter for when they can be used. I would have to wonder though, with just two wheels spinning like that how it would do in heavy rain? At least with motorcycles you can help keep the balance and keep the front end from going all over some. How would you keep one wheel from loosing its grip in this case and spin you around?
Somehow I can't picture this "car" or whatever you want to call it trekking through the snow we get up here in North America......