Because they're not much circulated.
Truly, that's it; I see these occasionally as old as 1995, where they've been just sitting around and haven't really been used and haven't toned. I suspect that at some point in these years, Lincoln's portrait was "freshened up" (sort of the way his wart disappeared when the large-head bills began and some of his wrinkles disappeared when we moved to colorized bills), and the result is this more detailed-looking, sharp, clear bust.
Truly, that's it; I see these occasionally as old as 1995, where they've been just sitting around and haven't really been used and haven't toned. I suspect that at some point in these years, Lincoln's portrait was "freshened up" (sort of the way his wart disappeared when the large-head bills began and some of his wrinkles disappeared when we moved to colorized bills), and the result is this more detailed-looking, sharp, clear bust.






















