Actually, the main purpose of sidewalks originally was to get pedestrians out of the mud, muck and horse poop of early, unpaved roads-- before there were cars or bicycles and before the rules of the road became standardized. When the first bicycle craze took hold (before the motor car was common or practical) bicyclists demanded, and sometimes got, both paved roads and bicycle paths, well before the creator of the myth that bicycle facilities are some kind of motorist conspiracy was even born.