Do you have kids? Kids don't make good decisions and trust takes time to build. Tracking kids is so the 'small mistakes' don't turn into something more serious.
The obvious question is "what did we do before?" I'm not sure how tracking stops serious mistakes; maybe it resolves them after the fact, suggesting that tracking their phone is not going to help parenting and you need another approach?
And yes, I do have kids of my own ranging from pre-phone to a brand new driver, so I get your motivation.
Agreed, and it's our job as parents to sheppard them. Handing them a skinner box and plonking them into the world doesn't solve that problem. And tracking then 24/7 isn't likely to help. Kids have been finding ways to get around their parents knowing what they're doing throughout all of humanity, and smartphones won't (and haven't) changed that.