That's a fair point, and I don't mean to insist that my way is the best way. It works for us, it surely won't work for all. But I am certain that with some effort on the part of the parents to be intentional, a good system can be reached. Our system continues to evolve, and with time and additional responsibility/freedom, will evolve eventually to us as parents handing complete control over.
that imposition of a lack of privacy just seems like a sure way to not only make them seek actual privacy elsewhere - moving their communications to other devices, and just doing stuff outside of "surveilled" devices or any devices at all, but to make it so that they won't ever share their actual private matters.
they will have their problems - just, outside of your reach, and they will not talk about them with you. (why? any reason, ranging from 'you don't get to surveil me - i'm going to have my privacy', to 'there's a looming possibility of blowback - I don't want to deal with that (or just, being afraid of that), so i'm just gonna keep my appearances neat (while doing real stuff elsewhere - and keeping that to myself')