Today’s obscenely obese iOS apps can drain a cellular data plan. It’s important to disable cellular data use in iTunes & App Stores.
It would be nice to be able to lock that setting lest an impatient family member drain the family plan. Unfortunately Apple’s Restrictions for locking cellular data changes don’t work on this. Bit of a bug really.
I suppose it’s too much to hope that iOS 11 will improve our ability to control cellular data use. It’s sucked for years. Apps don’t appear in the Cellular settings until they’ve actually tried to pull data down. Worse, an app added after cellular settings are locked defaults to data on — and it can’t be changed until cellular settings are unlocked. (A savvy restricted user with install privileges can remove an app that has no data, then reinstall it.)