alt Hacker NewsCars aren't the best option, but you can drop self-driving cars into an existing car-centric society one car at a time, with the car buyers paying for themselves.
Making a car-centric society meaningfully less car-centric requires the enthusiastic support of that society, along with competent political leadership, and probably a fair chunk of taxpayer cash too. Suburbs with huge lots make for long walks to the transit stop - but densifying those suburbs is not easy.
I don't own a car; I travel everywhere by bicycle and public transport - but the public transport I use was all built in the 1850s. Some time between then and now my society reorganised into a form that has a lot of difficulty delivering public transport projects.
This is a false alternative, because robocars do not exist, while public transit does exist but simply hasn’t been adequately implemented everywhere.
Politicians (and grifters alike) like to point to a future technology to solve an existing problem only to delay existing solutions which they don’t want to implement, most often for political reasons.