Unfortunately, yes. My brother-in-law discussed that yesterday with me saying that should definitely be added in IOS. That will prevent the thief from immediately switching the phone off, which then make the phone untraceable using the "Find My" feature. The moment we discovered that her phone was missing, I tried to locate it, but could not do so, assuming the phone was switched off by the thief.
That's just a short term solution for spur of the moment theft, there's nothing to stop career thieves from using faraday bags (apparently these do work) to block cellular and wifi signals and then later draining the battery.