(I'll add parenthetically that feet can - and often do - change in size and shape over the years. Yet most men figure that if their shoe size was, say, a 10D when they "stopped growing" at age 17, it's still a 10D now, when they're 20 years older. Many men go decades without having their shoe size measured on a Brannock device. I'm not saying that all men act this way, just that lots do. And I can tell you from personal experience that even a single letter difference in shoe width can be the difference between comfortable feet, and sore, aching feet. And that this is especially true with dress shoes - for various reasons, sneakers, moccasins, "casual shoes," etc., are often more forgiving of such things. I wonder whether this isn't one reason why so many men claim to find dress shoes uncomfortable.)
I spent 15 years of my adult life wearing and buying size 8.5, because that's what I wore when my I "stopped growing" in high school. It took the development of a Morton's neuroma in my left foot to get me into a Brannock device. I'm a size 9.5D in my left foot now (9D in the right), and the ill-fitting shoes I'd worn over the past fifteen years gave me a nice little long-term foot problem. Now SF is helping me build a decent shoe wardrobe in shoes that actually fit.