Even for the parents who know it's extremely difficult to really know if you're doing the right or wrong thing. And it's constant, you have to be eternally vigilant. My son brute-forced the downtime pin on his iPhone -- it took 6 months but he did it.
I truly am hesitant to ever criticize someone else's parenting style since if I've learned anything, it's that kids personalities can be very different and circumstances are always more complicated than you might think.
That said, I hear stories like yours (from friends) and it always baffles me because that's just now how our family operates. I have a downtime pin on devices for the same reason I lock the door to my car even though it's like 50% breakable glass windows.
My kids know the rules. One of them for sure knows the pin. But they also know that if they use the device outside of our agreed upon guidelines, they're in trouble.
I'm sincere in asking, aren't behavior controls a lot better than technological ones?
He absolutely got into trouble for breaking past the downtime pin. Although, not in that much trouble because I was honestly a little impressed.
Punishment and technological locks are both tools in the toolkit.
Ultimately you want your children to find the right balance with technology and that's difficult because most parents struggle with that balance. The world has moved very quickly and it is very hard to keep up. My kids are 12 years apart in age and they couldn't have had more different childhoods -- that's how quickly things have changed. Less than a generation.
And it even drastically varies between children. My two kids' (6 and 4) interests are vastly different which makes balancing difficult. My oldest is thankfully starting to understand that the rules apply to them equally. Consistency goes a long way.