Rome is a truly wonderful city, full of history and architecture. It is also full of cars, motorcycles and scooters. It was not designed for them; Mussolini tried to update the city and built a few roads like the Via dei Fori Imperiali leading to the Colosseum, destroying churches, splitting the forum in half, ruining the archaeology during construction and shaking what's left today in what has been called an enterprise more destructive than the sack of Rome. You can't build underground parking garages or more subways; there is just too much history below.
One would think that a response to this would be to promote alternatives like walking and cycling; the opposite is true, as they make it just about impossible to do either.