Two-wheelers in Paris-dise

Today I took the train from the small town of Breda in the Netherlands to Marseille, France. This involved 3 trains and layovers in Brussels and Paris. During my 1 hour in Paris, I spent 30 minutes at a sidewalk café near the Gare de Lyon, having a glass of chilled Kir and champagne and observing street traffic. From 7:30 to 8 pm, I counted:
• 61 bikes, 1 with child in a seat, 1 ridden by a child
• 27 Velib bikes, about 1/3 ridden by people wearing suits
• 16 Vespa-type scooters
• 25 motorcycles, 5 with a dual front-wheel design making them 3-wheel vehicles
• 10 Smart-sized cars
• 1 stretch limo
From this I conclude that Parisians are way into two-wheeled vehicles. I did not count cars or buses, unfortunately. I’d estimate a traffic volume of 7-10,000 per hour, and 15-minute bus service. There were bike lanes on both sides of the street, and noise levels and air quality were comfortable.

On a similar American street, I’d expect a similar mix, except with more SUVs and less bike traffic , but this proliferation of scooters and motorcycles is a European trend. They are cheaper to operate and easier/cheaper to park. They are also less polluting and take up less road space. I’m guessing they are owned by city-dwellers for cross-town trips, rather than suburban commuters. I’m wondering what the main driver is to people switching to these small and space efficient vehicles, and thinking it might be parking restrictions – perhaps the more scarce and higher priced the parking, the more two-wheelers you can expect.