You might be assuming the cameras work as they do in Switzerland.
In the US a common scenario is a private company installs the cameras for free and gets to collect most of the revenue. They adjust the yellow timing downward so that you don't have time to stop between the light turning yellow and it going to red. Then they send tickets in the mail to people who ran the light. Then if you do a study proving that they adjusted the timing downward to unsafe levels as a state sponsored scam, you get arrested and fined for "unlicensed practice of engineering".
In the US a common scenario is a private company installs the cameras for free and gets to collect most of the revenue. They adjust the yellow timing downward so that you don't have time to stop between the light turning yellow and it going to red. Then they send tickets in the mail to people who ran the light. Then if you do a study proving that they adjusted the timing downward to unsafe levels as a state sponsored scam, you get arrested and fined for "unlicensed practice of engineering".