I don't even think that it's lucrative per se, but rather that it's straightforward. Cop sits there playing candy crush, magical radar artifact makes a noise, t

I don't even think that it's lucrative per se, but rather that it's straightforward. Cop sits there playing candy crush, magical radar artifact makes a noise, they look up, chase down that car, then check a box on a pre-printed citation where they don't even have to think about which law to cite. But (real example) same road, clearly marked as trucks prohibited from left two lanes - a shed larger than many houses meanders by in the third lane, hanging well over into both the second and leftmost lanes - where do they even start? If the cop even happened to look up from their phone at the right time, they'd have to figure out which specific laws are being broken, how to cite them, what to take down as evidence, probably show up to the court date themselves, etc. So the actual hazardous moving violation goes unpoliced meanwhile every driver merely going the prevailing speed of the road has to spend a large part of their attention looking out for highway robbers laying in wait.