Originally Posted by dodge_mich

This was always my take on that rule (which I do follow):

Since pedestrians are generally going much slower that bike or auto traffic, this makes the pedestrian much more aware traffic that would impact them and give them a greater chance to move out of the flow of traffic or to take evasive action as needed.

A 25mph car or bike will come up on a 5mph walker very quickly, compared to a 20mph cycle. Likewise, a 20mph cycle can blend with traffic much better...