Maybe it's because Google and Microsoft and others' policy of security through obscurity actually succeeded in preventing the details of PhotoDNA from coming to light, and it took Apple exposing their hashing model to reverse engineering by including it on the device for people to finally wake up.
- PhotoDNA
- CSAM scanning on cloud photo platforms
- the acronym "CSAM"
Before this whole Apple client-side scanning debacle... seems pretty likely. A lot of privacy-focused people also avoid Google and Microsoft cloud services like the plague and trusted Apple up to this point to protect their privacy. The fact that Apple was (and is) scanning iCloud Photos libraries for CSAM unbeknownst to most of us is just another violation of that trust and shows just how far the "what happens on your iphone, stays on your iphone" privacy marketing extends (read: not past your iphone, and sometimes not even on your iphone).
"U.S. law requires tech companies to flag cases of child sexual abuse to the authorities. Apple has historically flagged fewer cases than other companies. Last year, for instance, Apple reported 265 cases to the National Center for Missing & Exploited Children, while Facebook reported 20.3 million, according to the center’s statistics. That enormous gap is due in part to Apple’s decision not to scan for such material, citing the privacy of its users." [1]
[1] https://www.nytimes.com/2021/08/05/technology/apple-iphones-...
I can tell you from working in this area that it's possible for someone to have their lives ruined by a misplaced investigation, have that investigation abandoned because they turn out to be obviously innocent, and for that to not be well-known, because people simply would not understand the context.
Before this Apple scandal, if you'd written to your reepresentative or a journalist or an activist group and said "I was framed for child abuse because of computer program that misidentified innocent pictures", they would attach a very low priority to dealing with you or publicising this. And almost all people who have experienced this kind of nightmare really don't want to re-live it in public for some tiny possibility of real justice being served for them, or for others. They just want it to all go away.