True. But it does create an audit trail that identifies 1) what phone made the call, and (assuming a newer phone) 2) exactly where it was at the time, and 3) where it is at any future time that it is turned on. You simply(?) have the network notify the authorities the instant the phone is switched on, at which point the perp is carrying a homing beacon.
I suppose in the case of a phone used to detonate a bomb those wouldn't be relevant. But would enough be left of the phone (assuming the bomb maker is thinking about such things) to identify it after the blast? In any case, the same argument applies to lasers, TV remotes, garage door openers, washing machine timers, alarm clocks, model airplane remote control gear, and a host of other gadgets that could be used to construct infernal devices, so we'd need ways to track possession of all those things as well.