Well....... if you had that, feet forward layout, like a car say, so the handlebars are quite a long way back from the front wheel, and you just put tellies on it, the rake angle would be huge, and it wouldn't handle nicely. The advantage of this layout is that the seating position is just like a car (without a seat rest) . The seat is the same height as my family car. At that height, you are 2/3 the height of a 'normal' bike, and the same width, so your frontal area is 2/3 of a normal bike, so it has 2/3 the drag, so it goes faster. That said, the wrong way round steering self-steers better than a normal bike and it feels really secure, especially on very tight turns. I even made a two wheel skateboard with the steering axis the 'wrong' way round.
https://youtu.be/5MQ7qDzfENo You can see that it steers the same way you lean - even without handlebars. If you used a 'right way round' steering axis angle, it wouldn't work.
inline longboard - for on and off road
I know the bike is very small, but its lighter and faster than a 125 Honda say. They're about 130kg. Mine is 80kg - and the scales don't lie. Big scooters, like Yamaha's Xmax for example, are quite feet forward, but to get a proper car-type seating position, the rake would be too big and they wouldn't handle. So, they are still quite upright and have more drag than my bike, (and weigh more too, but that's probably not a fair comparison). They should use my front end on big scooters. They would handle better and go faster.
So, I suppose that's the answer to your question, why? It bike handles better and goes faster than anything comparable.
