You are neglecting the part where major roads in the suburbs are aggressively unsafe if you are on foot or on a bicycle. There are places that are theoretically ten minutes away from me that require biking along the edge of a four-lane street with no side parking, no bike lanes, and no sidewalks, and a constant stream of cars to fight with. Biking or walking through that shit is super dangerous; I stay in the parts of the city that have roads that have some hope of the car-drivers acknowledging that the road belongs to cyclists, too.
