PolitiNerd saidOne word:
Why? You don't need cars in big cities. Public transport is easily accessible and get you everywhere.
People want to get where they want on their own time. Public transport is handy, but on an all-the-time basis? I don't have my license, so I rely on public transport. When you have things like waiting times, track work, coordination of getting things done, predetermined dates, changes to the public transport, things ate almost impossible to do well.
That's why people have personal transportation. To go where they Wang when they want. Circumstances allowing, of course.
So, again; everyone in Hamburg without a car in 20 years?FANTASY
EDIT: Also, public transport doesn't get you everywhere. Even in a city like Sydney, you can be getting trains and buses and still be kilometers away from where you actually need to be.