Maybe. Many people (particularly parents) in suburban areas store a substantial amount of equipment in their cars, and can't effectively use a taxi-service. If I had to pack everything my kids need in a day in and out of shared car at every stop, it would add 10 minutes to each leg of my trip. Plus, do I haul the stuff I bought at the store on my way to work into the office so that my self-driving car can go somewhere else? What about my kid's stroller? That lives in the car.

In urban areas, people travel light, but that's not the case in sub-urban and rural areas.