Roads existed long before cars. Even the Romans had paved roads. That is not a valid argument. The reason people took a long time to take up cars was cost.

Roads existed long before cars. Even the Romans had paved roads. That is not a valid argument. The reason people took a long time to take up cars was cost. It took time for cost to come down and reliability to go up. Once that happened, they were adopted widely. Even then, it took a long time for cars to disappear. Any photo of San Francisco around 1915 or so will show plenty of horse-drawn vehicles on the roads, and cars will be present, but scarce. This is 7 years after the Model T entered production. abruzzi has answered this well - not everyone can afford a self-drive car. They will not be cheap initially - far from it, in fact. I'll grant you that the cost-reduction time will be faster in this instance - nobody has to invent the modern production line - but the cost of development and warranting of all the parts will be expensive. Replacing the vehicle fleet takes at least 10 years. Replacing it with self-driving vehicles could easily take twice that long, even if you started today, which we are patently not.