Police departments say they work, sometimes amazingly well. Violations drop from thousands to hundreds. So cops and local governments want to put in more of the things. Like complications in the tax code, like most things governments do, the idea makes sense in the short run. Lots of people, including me, are tired of nearly being hit by people who blast through lights.
Cameras are cheaper than cops.
Thing is, cameras are getting not just a little cheaper, but lots cheaper. So is networking, to connect cameras with computers downtown. Now we have them mostly at big intersections and those that have been particularly dangerous. Putting them pretty much everywhere is not a technical challenge, and what works tends to be done. A few days ago I was waiting for a break in traffic to cross a street that had a camera.