I think that there is a big difference, for the population, between "somebody is reading and keeping a copy of all your mail" and "Some algorithm looks for illegal material locally on your phone. If you don't have illegal material, it won't do anything".

Nobody would want to carry a microphone recording them 24/7 and storing everything on a server, but everybody is fine with TooBigTech simply promising that they don't store the data.

We have to accept that people are fine with the idea. The problem (both with the connected mic and ChatControl, btw) is that it can be abused. That's the problem. Again: we have to convince people that it is at risk of being abused. Not that they should be outraged. They just are not.