Typically the world changes when a new market is discovered, making the earth more traversable by car at the time opened up enough of a new market that it was done post haste for better or for worse. The only real way I see self-driving cars opening up markets at a scale that they would justify the amount of overhead is if they created self-driving only lanes with infrastructure closely around them to be quick and easily accessible from the passengers.

Which at that point is really just the Japanese train system and surrounding infrastructure, which many places (at least in the US) don't seem capable or willing to make happen.