The purpose of traffic laws are twofold:
1. enable traffic to move as fast as possible.
2. Enable traffic to move as safely as possible.
The laws are a blending/compromise of those two somewhat contradictory goals. “Safe” is a relative term. The roads would be safer if the speed limit EVERYWHERE was 35 mph, but it would severely violate the first rule for marginal improvement in the second.
And the simple fact is that passing lane nannies result in road rage. This is a dangerous condition. Preventing them from doing this will make the roads actually safer for that reason and others while, at the same time, increasing the speed of the flow of traffic.
It is a win-win.