The lack of black characters doesn't go "conveniently unnoticed" by black people, or rarely (in my experience) Asian or Latino people. Only white people don’t usually notice this lack of diversity because the "norm" is for the main characters in comic strips, cartoons, young adult fiction and even K-12 literature to be white. I was a K-12 editor for many years and was always surprised when I saw non-white people in the books.
It starts with whoever is writing the book and whether the editor or graphic designer makes any kind of suggestion to diversify the images. But it really starts on the publishing end with publishers giving minority writers an opportunity to show larger representation. In a world where people can self-publish, that helps. But to get self-published and diverse books included into a K-12 system, it has to be (first) well-done and (second) introduced to someone who is in charge of ordering bulk copies.
I’m going to go out on a limb and assume if “Please, Baby, Please” is read out loud in kindergarten or pre-schools, it’s probably not from non-black instructors.
P.S. I didn’t know who Addy was so I looked her up. I see a whole helluva lot about slave life and plantations. Again, every single black character in these books seems to be tied to slavery somehow, Mark Twain included. What I wanted in school was just black kids, black girls specifically, just living their lives. I just wanted them to be living their damn lives and enjoying their childhood, not daydreaming about freedom. It’s great that she won a spelling bee, but at that age, I would’ve much rather read a book about an Akeelah and the Bee — just a black girl growing up. That’s it.