Quite right, maybe we should all travel everywhere at 30mph?
Very few people are capable of travelling anywhere at 30 mph these days. It's much more difficult than doing 90 on a motorway.
iirc, no-one has been caught by the M25 cameras in over a year now. I've travelled the M1 a couple of times in the last month and noticed little regard for the enforced limits, and not seen a camera flash
Not all cameras flash:-
Truvelo Speed Cameras
Truvelo system is steadily becoming more common and some parts of the UK now predominantly use this type of camera. Three white lines are painted just ahead of the Truvelo camera and there are strips in the road that register the speed of the passing vehicle and trigger the camera.By using an infra-red flash, the Truvelo camera avoids the flash that the rear Gatso cameras produce when a photograph is taken. This means that the driver doesn't see a flash but the camera can take a photograph of the driver, as well as the front of the vehicle.