Whats your point here?
You just told us that when people see cops, they jump on the brakes, but as soon as they are out of sight they'll get straight back on the gas and go the same speed that they were originally doing (that includes doing over the limit if they wanna). How is that making anything safer, and how is it teaching anyone a lesson about speeding?
If they dont get caught, they wont learn. It doesnt matter if the cops are hidden in the bushes or not, they need to be caught in order to really slow down in the future.
The police will always have a bad name because they are the authority on the roads. No matter what circumstances you get caught speeding in, your still gonna be pissed at the cop that hands you the fine.