I thought it was self evident. Normally cars sit in a garage for most of their lifetime, potentially with added cost to deal with expensive parking. You buy a car because it's prohibitively expensive (and not as convenient) to either share or catch a taxi all the time. You share someones car driving it to work, how does the other person use it for the remainder of the day? There's no easy way to make it work.
These dynamics change with self driving cars, you can have on-demand, and cheaper (amortized cost would be the fraction of the cost of ownership). The only issue is availability at peak times, but most of the population can work around this - indeed if you could save $50k by getting to work 30 minutes earlier every day, the average person is going to go for that.
