This article by an experienced former police officer makes many good points. Sadly, most of them apply far beyond the context of traffic law, and are also relevant to other parts of a legal system where pretty much anyone can be arrested for just about anything.
A few especially noteworthy points:
"When I was a recruit in the police academy a lifetime ago, I remember an instructor telling our class 'If you are following a car for more than three blocks and haven’t found a violation to stop it for, then you just aren’t looking.' He was right. None of us are capable of complying with the entirety of the vehicle code for any length of time. That does not seem to make much sense. The entire goal of policing is to gain voluntary compliance with the law—something that cannot be done if the law cannot be understood or followed by the average person."
This problem is not unique to traffic law!
"As a revenue generator, traffic tickets are a local politician’s best friend. They can be increased as needed by a simple order from the top that enforcement be stepped up. There is no shortage of violations and violators to cite…ever. Lest anyone complain, the response that “it is for traffic safety” shrouds the politician in an unimpeachable blanket of righteousness by looking out for our families, especially our children. We need a law against that crack in your windshield so that we might save just one child."
Lots of other types of law enforcement are also potential cash cows for local and state government, and also feature massive discretion by the authorities (as the list of potential violators is almost endless).
The author recommends, among other things, that we should be "Reevaluating the traffic code and identifying where enforcement really does enhance public safety, such as DUI’s or reckless driving, in order to have a code that can be followed by all motorists all of the time."
We should similarly reevaluate - and in many places pare back - the rest of the legal system, as well.