This article speculates that that's because Apple is not scanning on iCloud to respect their privacy policy: https://www.hackerfactor.com/blog/index.php?/archiv

This article speculates that that's because Apple is not scanning on iCloud to respect their privacy policy: https://www.hackerfactor.com/blog/index.php?/archives/929-On https://www.hackerfactor.com/blog/index.php?/archives/929-On... Apple's report count to the NCMEC is really low so it's probably true that they are not scanning on iCloud unless they receive a warrant.