There is also the convenience factor. I do remove my battery frequently from my phone but it is too easy to just leave it on. People will generally not want to

There is also the convenience factor. I do remove my battery frequently from my phone but it is too easy to just leave it on. People will generally not want to hassle with it if they don't have to.If security is easier and requires less effort then it lowers the cost and will be favored more often and it will protect more people. There are also many times that people have been unhappy because I have my phone off and unable to reach me. There are also other times you want to be available. Unfortunately, if your phone is owned then they can just exfiltrate the data when normal data transfer occurs. The data will still need to be stored for transmission later though. With the iphone, you also need to monitor Bluetooth and WiFi in addition to cellular activity. Hopefully they will also monitor these.