You can hop on a plane and go from a driving-city to a walking city, look around and see the difference. I can't accept that this doesn't matter.

It's a whole lot easier to hit up a drive through or grab a tub of ice cream at the grocery store when you're driving a car.

You're not wrong, though. Walking around doesn't burn a lot of calories (~100/mile), but most people become overweight by only slightly overeating on a daily basis, over a long period of time. One can of soda has 140 Calories. 140 excess daily Calories is an extra pound of fat per month.