People that bike, walk (or roll, in the case of wheelchair and electric scooter users) share sidewalks every day, and the combination of modes can cause conflict and confusion. Oregon law, however, is very clear on right-of-way and the legal conduct required when you are bicycling on the sidewalk.
Legal clarity aside, the devil is in the details.
One problem is that bicycle operators travel much faster than walkers and require considerably greater distance to turn and stop. When bicycle traffic is constricted, such as on bridges and other multi-use paths, the inevitable congestion magnifies the impact of the small steering or control mistakes that lead to occasional collisions.