Mobility issues aren't going to be the same for all people as they age, but too many people live in areas where not being able to drive will essentially be a home prison sentence. Obviously walking and public transit might not be great options for some of those same people - inability to drive might be due to reasons that make those activities impossibly hard too - but living in a place where calling a cab won't bankrupt you, and where many needed things are a short cab ride away, probably would be.
