[vinay427]

Assuming we're not talking about the extra-wide sidewalks common in city centers which sometimes also host designated bike lanes, ordinary sidewalks that I've seen throughout the US and Europe are nowhere near wide enough to fit even a single cyclist passing alongside a pedestrian without a risk of collision. Add multiple pedestrians walking alongside each other, other hazards such as parked cars, less competent cyclists such as children, or pets (on or off leashes) and it quickly becomes a recipe for disaster for one or both of the sidewalk users.

Also, bicyclists in cities tend to travel closer to the speeds of cars than pedestrians, and tend to have more similar dynamics such as turning radius and stopping distance which infrastructure for cars is already designed around. Additionally, car drivers are licensed and there is an expectation of awareness that they must exhibit. This makes it far easier to place slower-moving "hazards" in their path than adding faster-moving vehicles in the path of pedestrians.