I think of that when this topic comes up. There really are shades of "black" that reflect different highlights.

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To complicate matters, comics are full of colors not found in Nature. Batwoman in the Fifties worse a costume that was black with yellow highlights. Daredevil was occasionally black with red highlights. Storm wore a shiny black costume with white highlights, and animators made it white (even after asking me!). In my 3D modeling, I have leaned to use the specular setting to vice shiny black objects highlights they'd be most unlikely to have in real life.

It's all about playing the game.

In many cases, characters went from black to blue because of deadline pressures. Black spaces take time to fill in. Empty spaces don't. Every minute saved when chasing deadlines can be important.

And sometimes the inkers were given what today would be called breakdowns, with no blacks spotted. Sometimes inkers ink just that, and we get coloring books.

And there is that extra annoyance on top of these, and that's when mistakes become carved in stone. "This is how it was done last time!" "But last time it was wrong!" "But this is how it was done last time!" (And Brawndo has electrolytes...)