Pedestrians and cyclists can be killed or seriously injured in a collision:

https://www.independent.co.uk/news/uk/home-news/cycle-safety...

A pedestrian was killed by a cyclist in my city (Perth, Western Australia) on a shared (bikes and pedestrians) path some years ago.

The argument that broken bones are the worst outcome of a cyclist-pedestrian collision is incorrect.

Apart from human error ("failed to look properly"), the second most common factor in car-cyclist collisions is whether the cyclist is entering or crossing the roadway:

https://www.rospa.com/rospaweb/docs/advice-services/road-saf...

In other words road crossings and riding past driveways across the sidewalk increase the risk of car-cyclist collisions considerably. As a commuting and recreational cyclist, my personal experience aligns with this strongly. Most of my close calls with cars have happened when I have been riding on a designated cycle path (separate from the road) and had to cross or enter a road.

So riding on a sidewalk that contains numerous road crossings or driveways can increase the risk of a collision for the cyclist.

In Perth we have a network of "shared paths" for use by cyclists and pedestrians. These are wide paths with a center line marking (ie they are for bidirectional use, convention is to keep left) and are separate from the roadway. Until very recently, adult cyclists were not permitted to use other sidewalks/footpaths unless they were accompanying a child cycling.

On these shared paths pedestrians always have right of way (even if they are on the wrong side of the center line). If a cyclist hits a pedestrian, the cyclist is considered to be at fault.

Why?

Well these paths are often through public parks or along scenic sections of the coast or river bank. As such they are popular places for families to take their children and to walk their dogs. Young children and dogs have no concept of "keeping left" and may do unpredictable things. As cyclists are the faster moving path users, it is their responsibility (by law) to enure they can safely pass pedestrians. Cyclists must have a warning device (bell or horn) to warn they are approaching and if it is unsafe to pass must slow down or stop until they can pass safely. Dog owners are required to keep their dogs under control (I think they may be required to use a lead by law, though many don't).

Most other sidewalks here are not designed for mixed use by cyclists and pedestrians. They may not be wide enough, have no designated center line marking, may be in front of retail or food outlets (increased pedestrian traffic with added unpredictable stopping/direction change) or have numerous driveways and road crossings.

Children, the elderly and dogs are common users of sidewalks. Children and dogs often make unpredictable moves on paths. The elderly are generally less agile (unable to take evasive action to prevent a collision), have diminished sight and hearing and are at high risk of serious injury in a fall or collision.

As a regular cyclist, I choose to ride on the road over the sidewalk as it is more efficient and safer for me and others (even though I have been hit by cars a few times). Where possible I will use a shared path, but often elect not to as they are too heavy in pedestrian traffic (coastal paths) or have numerous road crossings.