If we assume self-driving cars will be an on-demand service, they could be offered intermittently - only on good weather, at daytime, at cities(or even routes) already mapped. Even with that limitation, it could be a pretty valuable service, if complemented by the right ride-sharing services.

And even when purchasing a car , a car that "only" drives itself when it's safe would be great, even if it's only 40% of the time, for people in the right city.