I’m not talking about a traffic jam. I’m talking about a full highway at normal highway speed. By full highway, I mean all lanes contain cars spaced approximately “assured clear distance” or a little less, and by normal highway speed I mean 60-70mph on a two-lane divided highway. “Left lane for passing only” does NOT work under those circumstances, which are quite common in many areas I frequent. The highway runs just fine as long as we don’t have any idiots in either lane moving significantly below or above that speed range. The tailgating, lane-weaving idiots clearly do expect “Left lane for passing” to be enforced, and get quite irate when it (invariably) is not.
My point again was only that because it does not always work does not mean it is not the best in general but I am sure that you are a courteous driver who yields to the faster cars as much as possible.