Each generation of stamp collecting is defined by the wants of (what I call) movement collectors, that is the serious collectors of that generation, traditionally mostly older men who do most of the buying and selling in the hobby. These movement collectors are largely men who have gotten back into the hobby in middle and older age and they are usually trying to create collections of stamps they couldn’t afford in their youth in quality grades that were unobtainable with their juvenile finances. Thus we saw the collectors of the 1980s and 1990s bid up the prices of stamps of the 1920s and 1930s, the ones they couldn’t afford when they collected as kids in the 1950s. And they wanted those stamps in only the best Never Hinged quality because those stamps were unaffordable to them in that quality when they were young.
Movement collectors of the next generation will be coming back into the hobby with a far different agenda. Every stamp issued from anywhere since WW II is far more common NH than hinged and perfection in quality for this next generation won’t be as important as it is now. And future generations? They have been weaned on stamps that didn’t even have gum (the self stick adhesives) and so, if history is a guide, may well not even care about the backs of their stamps. Keep in mind that these generational trends among each era’s movement collectors has held true for over century and when you pay such a big premium for early NH stamps you are indulging a generational prejudice and not following some ironclad philatelic law.