The long answer is cuz it's too expensive for cities to set it all up with the technology and making it work. The short answer is bc they got a sweet deal and they're raping the city.

I think it was San Fran or Oakland that had an intersection where they installed a camera and brought in $200,000, but billed the city $175,000 for it, so the city bragged they made a profit of $25,000 which might be good enough for government work but I see it as the city lost enough money to hire 3 more cops to keep the streets safe. Hell they could stand there and do tickets by hand for that price and it would still be safer.