I should have mentioned that I live in europe. By US standards, our cities are extremely walkable. That being said, I have three super markets that I regularly buy from. Two of them are in walkable distance (when carrying few groceries). For the third, cheapest, I have to use either a car or a cargo bike.
Not everyone lives in the big city. Not everyone needs to. Even within the big city, there is lots of room for improvement.
And making it possible for more people to run some of their errands on foot doesn't mean "You aren't allowed to leave this 5 square kilometer area and can never drive or use public transit." It just means some of the things you do normally can be reached on foot (for a greater percentage of people than is true currently).