In my very humble Italian opinion, the reason why scooters are so popular is very simple: our economy is too trashed to let most people drive decent cars: a scooter (at least one with a real scooter displacement and features) is 1) as "cheap" as (or cheaper than) a bike; 2) more suitable than a bike to go to work wearing a jacket and tie; 3) practical in the winter, when you can go out in the rain (as opposed as taking a car that you don't have or uses half tank of gas to go 5 miles in crowded downtown); 4) and, above all, gives you a very high gas mileage in a country where gas is almost 4$/gal.