While there are always “exceptions to the rule” there are many elements of human conduct that are ruled not by laws or regulations, but rather by common courtesy, ethics, self-interest, and social habits.
Adherence to these unwritten patterns of human interaction is typically more consistent and predictable than behavior dictated by government edicts and orders. For example, if one stranger greets another stranger with a simple “hello” or “good morning” it would be extremely rare that the other person would not respond in a similar manner, even if only to nod or smile. To do otherwise would be considered rude and unfriendly, but it is not illegal.
The same is true for interactions between motorists, unfortunately, the insulating quality of an automobile retards or distorts these interactions.
When motorists enter a construction zone where two lanes narrow to one the natural pattern that evolves is that the drivers take turns entering the single lane; first from one lane and then from the other lane. No law, just a common courtesy. The same interactions take place when vehicles enter and merge onto limited access and divided highways.
The point is that much of our driving behavior is really dictated by patterns that have evolved over the past century. These patterns are now part of our driving ethic. Lane courtesy, the practice of yielding the left lane on multi-lane highways to faster and passing traffic, should be part of that ethic.
Laws that require the practice of lane courtesy are helpful in that they provide a platform to promote lane courtesy and to educate the public on the benefits of this practice. As enforcement devices (like many traffic laws) they are of marginal value and they are difficult to enforce.
For lane courtesy to flourish it must be accepted as the ethical and right thing to do, not because it’s the law.