system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is it supposed to be "safer" for cyclists to be on the edge of a busy street as opposed to a sidewalk?

I cycle recreationally from time to time, and in my area the dedicated bike lanes are right along the side of 60-80 km/h streets that are usually very busy. Why is it safer for a cyclist to be there as opposed to on a sidewalk?

As a driver, I find it frustrating to try to dodge cyclists (especially if they aren't as far over as they can go), and as a cyclist, I hate having to watch over my shoulder every five seconds to see if a car or truck is coming.

Edit: Thanks for all the information, everyone. Some information I hadn't considered. Thank you!
gpt
In California, cyclists who ride slower than other traffic are supposed to ride 'as close as practicable' to the right-hand curb or edge of the roadway.
A cyclist, being closer to the road, is a better judge of the actual road condition (glass, stones, other debris, etc.) than a motorist driving a car, and so a cyclist will typically ride farther away from the curb than you may think is appropriate.