Ah, but there is. Privacy.
Tell that to the masses who post their entire private lives on bookface and tictac. The overwhelming majority of people don’t give a fuck. Especially if it means having to give up all their favorite apps.
I don't know why you think you have the moral high ground here
What makes you assume I think that?
there are people who don't like being part of a surveillance economy, and as paid-off lawmakers aren't going to do jack shit
Of course there are. The question was why mobile OSes that offer that don’t take off. And the answer is simply that very few people care enough for it to be a viable market. Very few people care enough to be willing to get excluded from iMessage or Facebook groups just to take a principled stance on privacy.
If you want these to take or you have to offer way more than some abstract promise of better privacy. Think of what you’re asking people to give up. To get them to switch you need a massive incentive.