Why I need WiFi to update iPhone?? Why not use my mobile data ??
I need my phone use mobile data to update my phone.
Question marked as
iOS updates tend to be larger download files that require more stable bandwidth than some carriers provide. Customers who only have 3G data connection or less would not be able to receive the update successfully without wifi.
Here is a support article with more information: https://support.apple.com/en-us/HT204204