Okay, but counterpoint: why don't these school libraries also remove for example the Bible, a work known for extremely graphic content, eroticism, calls to kill based on one's tribe and doing stuff like working on the Sabbath. It's also a book explicitly meant for indoctrinating children into a given religion, or actually one of two religions!
These principles of what is good and age-appropriate for children doesn't seem to be applied consistently.
Well apparently at least public school libraries in Utah's Davis County[0]. To their credit, they did actually ban it due to vulgarity and violence, so at least they were principled in that sense, but then the book was brought back due to backlash.
Because it is an historically important work that is necessary to have some understanding of to understand large parts of history. Its purpose also is not indoctrination or titillation.
These principles of what is good and age-appropriate for children doesn't seem to be applied consistently.