It's typically included on lists because of the implications. One either takes the position (1) child pornography should be allowed to be shared, (2) child pornography should be suppressed, but may be shared, or (3) child pornography cannot be allowed to be shared.
(3) obviously requires very different technical solutions (like: no private encryption, ever) than (1).
(3) obviously requires very different technical solutions (like: no private encryption, ever) than (1).