> At some point, there’s going to be a large number of cities where a majority of homeowners are too old to drive.

If you're too old to drive you're probably also not in the best position to walk far or walk while carrying shopping/groceries. Combined with the obesity epidemic many people simply aren't healthy enough to walk 1km.

Mobility challenged people can take electric wheelchairs along sidewalks and bike routes, and board buses and trains with level boarding. These usually have storage for groceries. Some elderly people are physically capable of driving a car but can be a danger on the road.