1. The apps used MDM profiles, intedned for control of employee's smartphones and/or vpns to filter access to apps.
2. Those approaches gave the app makers enormous control over the devices. If they used vpns, all internet traffic from the device could be intercepted. If they used MDM profiles, they had deep access to all the device's settings. It was a huge privacy risk.
3. This was clearly against Apple's policies. APIs were used for the purpose they were not intended for. That was what Facebooks's certificates were revoked for. They should've feared removal since the day they wrote their first line of code.
4. I guess that Apple understood the need for parental control apps and allowed them, with the privacy risks, as there was no other way to get parental control at the time.
5. Apple knew how important iPhone addiction has become and developed their own, privacy respecting solution, screen Time.
6. The need for parental control has now been filled and the privacy risks of those apps now outweigh the benefits. Apple made the decision to remove.
7. Apple, in general, doesn't allow other apps to access such information on your device, for privacy and security reasons. It's a bit anti competitive, yes, it limits what app makers can do, but it makes iOs secure. There's no other way to do it, and that's what many people don't understand. Apple's philosophy sacrifices some features you might have for your own security. If you're not fine with it, use Android and sideload, but don't run screaming to the police when it suddenly turns out that the online banking app you've just installed was a very good fake. [1].
[1] https://www.tahawultech.com/industry/technology/android-warn...