Just because Apple willingly avoids knowing what their users store on iCloud does not mean they are taking the active role of allowing illegal content to be stored.
(1) Streisand effect (mentioned by another commenter) - it would generate tons of free publicity for their opponents.
(2) Civil discovery - the defendant would get to demand access to Apple's internal e-mails about this issue in order to try to prove its case.
(3) Possibly losing - even though this feels obviously intended to make people believe false things about Apple, a court might accept that there is some interpretation of "allows" and "complicit" that are protected criticisms of the company under some jurisdiction's defamation standard.
Encrocrypt and Cyberbunker probably had terms saying not to do illegal things...
What matters is how they respond to problems as they are pointed out. If it would turn out that links to their hosting service keep popping up in child abuse cases, do they respond by deleting them piecemeal or do they put a system in place that tries to identify the content by fuzzy hash and flags it for proactive review? Do they actively cooperate with the countries' law enforcement where the picture got uploaded from? That sort of thing. That has infinitely more impact than "you wouldn't download a car" notices