Because adding surveillance placards to one of the few remaining untracked modes of transportation is a fantastic idea.

This "make cyclists stop" red herring persists because some drivers have developed stockholm syndrome with the large quantity of unnecessary traffic control devices that have been deployed by committee (most stop signs could be yields, most red arrows could not exist, and at least a third of stop lights could be simply eliminated).

Cyclists are much more in touch with the life and death reality of public roads, because even when following all traffic laws they can easily be killed. Competent cyclists treat red lights and stop signs as yields because there is no downside for anyone - just like drivers who do rolling stops.

And yes, incompetent cyclists exist just like incompetent drivers exist - if you want to defend yourself from being wrongly blamed for an accident with a self-endangering moron in any vehicle, get a dashcam.

I just call it as I see it. And in every American city I have been in in the past ten years, I would say a good 95% of cyclists who come to a stop-sign intersection just run right through the stop sign never slowing down, regardless of whether there are cars at the intersection or not. Don't take my word for it, go out and watch. Go to any intersection in any city. Wait for a cyclist. Bingo. Next cyclist. Bingo. Try it. Basically almost all cyclists run stop signs. There is no red herring. It's the culture.