Cars are mostly useful for larger distances, i.e. on highways, where slow vehicles are not allowed.
The main limit is carrying capacity - maximum power - and you really do not need that much stuff. This works long range too, and could work even longer range should there be proper cargo trains for bikes. But there aren't.
The trip time is typically needed to be less than 10h or you need alternative driver or a long break anyway. A car can go let's say 1000 km on average in that time. A plane maybe 5kkm and a train matches a car. A human powered bicycle goes perhaps 250-300 km. Man on foot goes 40 km.
In a city a car is on average 30% faster than a bike and even less vs a scooter or motorbike.
Except in the bigger mode of transport there is space to put in amenities and a spare driver or secondary crew.
Just like the flying pigeon bike was massively popular in china back in the 70's, I even saw one being ridden at Cranfield university by a Chinese masters/doctoral student in the late 70's early eighties.
And even if not, what would you gain with these weird single purpose vehicles that can't be used while remaining in comfort and need to be replaced every winter over a multi-purpose super-comfortable shared microcar? It's not even economical or ecological, ordinary bikes/scooters + microcars + public transport is the ecological/economical solution.
In Japan, bicycles routinely have child seats, and frequently two child seats (front and back).
Where I live, people tend to ride motorbikes on a weather permitting basis. Which means the bulk of days are in late May, June, July, August, and early September. Assuming they can afford to have a second vehicle.
