This is because Apple has recently released the iOS 11.3 update except that the update is only available for Apple’s new iPad. It is an odd move considering that Apple typically releases updates for everyone and all at once, and hopefully this isn’t going to be some new move by Apple where they release updates in stages as it could result in fragmentization like what we’re seeing in Android.
It is unclear why Apple released it for the new iPad first, but the upside is that if Apple thinks the update is ready for the new iPad, then it should probably be ready for the rest of Apple’s eligible devices. Hopefully this means that a global release shouldn’t be too far behind, but when exactly that will happen remains to be seen.
Some of the changes made to iOS 11.3 include the ability to disable throttling. It will also include a battery health feature which lets users know the status of their battery’s condition, along with some changes to privacy where Apple will make it clearer when personal information is being requested.