You should see in some asian countries the number of scooters on the roads ! Indonesia, Vietnam, Thailand, South Corea... There are scooters EVERYWHERE in cities, way more than cars.
That is due to the fact that there is not enough space for cars for that much population, most of time public transports are bus, (slow), weather is fine, this is a cheap compared to owning a car.
Here in Europe people commute with scooters for the same reason, too much traffic, people get sick of waisting so much time. In my opinion we (in south Europe) have been influenced by Italians since 60's, Vespa was growing ans spreading all over south Europe, with a cool attitude image.
On the road riders and car drivers don't get on very well, especially in big cities, at least in France and Belgium !
I use the scooter here in Brussels because it's so easy (despite the humid weather) compared to car or poor public transportation. As I work in medical and have to travel from one hospital to the other for emergencies, I have no choice ! I used to ride a big motorbike but switched to scooter for obvious reason, practicality.