For basic traffic enforcement, you're right. However, poor implementation in the US has led to withdrawal of systems in some cities. I'll have to dig up details, but I recall a red-light system that was implemented as a revenue-share with the company contracted to build/maintain the system. That company set the timing of the camera such that it had many false-positives (it was basically triggering on yellow instead of red, IIRC). System was eventually shut down, but people are now rightfully wary of similar systems.

But, my comment wasn't meant to imply traffic is the only place this happens, it was just an easy example. We see the same with (building) code enforcement at all levels from HOA to city/town/county. We see excess policing/enforcement (to the point of infringing on individual rights) in certain neighborhoods and with certain ethnic groups (stop and frisk in NYC, for example).