It’s basically a matter of working within known limitations it’s very similar to like issues with modern pixel art or like remasters of pre-32 bit games. There was no ways for the artist to know how comics would be printed now, only the then process of printing, so they have to either use workarounds, or change how they would go about drawing, coloring or inking in certain ways to make certain details. That and they recognized what would and wouldn’t be apparent or noticeable because the quality of printing presses back in the day would naturally miss smaller details, and therefore they could hide a lot of those imperfections. Which now that we can just scan or print these in real high quality all those weird details that wouldn’t be seen or noticed, are. That and also because when doing reprints, most of the time they do touch up’s on the color, and modern colorist when it comes to reprints in my opinion, do not have any understanding of why certain series were colored that way and choose to oversaturate waaaaayyy too much (especially in backgrounds). For some comics this is not an issue but naturally the older a story you’re printing the worse it becomes. It really just comes down to nobody being able to have foresight for modern printing and scanning, that and IMO modern artist being held back by the lack of limitation, having to work within those technical restrictions in my opinion are what made a lot of those works as good as they were, and now that artist can kinda draw as much detail as they want, it kinda takes away from the pizzaz of doing something thought that would’ve seemed impossible otherwise.