Why?
Because the Mormon moms don't want their innocent teenagers to be corrupted by the sex in the book.
Some moms successfully got October Sky (Rocket Boys) successfully removed from the summer book list because the teenage boys engage in very mild locker room talk and once more part of the book.
I am not making this up.
For the record, I love both books. In 1984 is one of my all-time favorites. It is a vitally important book in any time, but seems especially fitting right now.
Oh, and it was assigned reading at The first school I taught at in California back in the early 2000's