Traditional public transit only works for the geographically privileged. If you don't live along one of the few transit routes in a city, it doesn't work, and even when it does it can be quite inefficient.

In contrast, self-driving cars scale quite well especially to rural areas. They are point-to-point and on-demand. Low cost to operate compared to traditional public transit means that even rural cities could have a self-driving car based public transit option.