In the US speed cameras are viewed as revenue generating devices, instead of devices meant to protect the public safety. So most places have laws against them because the voters see it as “you just want to charge me for speeding” instead of “people breaking the speed limit are unsafe and need to be stopped”. So instead speeding is mostly enforced by actual police on the road (or pulled slightly off the road) using radar guns. The idea being if you were speeding enough to make a policeman bother to turn the siren on, track you down, and issue the ticket, you must have been doing something pretty unsafe.
There’s actual history of revenue generation by camera, legitimate reasons for suspicion. Plus it violates any right to face your accuser. Plus it probably doesn’t even help safety with the delayed feedback: you’ll slow down as soon as you see a cop, but would be speeding for weeks before seeing mail from the for-profit company managing the speed cameras. With the lack of feedback, you could be looking at dozens of violations before you discover there is a problem, which doesn’t help anything except maximizing revenue
I think the right to face your accuser is probably the biggest one.
As far as the lack of feedback goes, I can say having driven in Europe plenty of times that the cameras are extremely effective in getting drivers to obey the speed limits, but it’s not the cameras themselves - the the knowledge thay they exist. Entering a 10km stretch of road that has signs posted everywhere saying “average speed zone next 10km” or something like that, where they snap a picture record the time of you entering the zone, then a picture and record of the time when you exit it and calculate your average speed. I’ve seen 5 lane wide roads full of cars just chugging along at 2km under the target posted speed. So for that I will say they are extremely effective at maintaining large numbers of cars at safe speeds.
Once the cameras have existed long enough, everyone knows they work, because everyone has gotten a ticket in the mail. That’s when the posted signs of “camera ahead” really work. You’ve played the game before and lost, so every future opportunity will now have a giant red flag on it in each person’s mind.