Because the Taliban carry cell phones....
and they move at night. That afforementioned standby mode means that effectively any Taliban tosser carrying a cell phone can be tracked by his cell phone registrations at each site. Hey you could even get some idea of how fast they are moving by calculating the time taken from one to another. Once you have ID'd some lurking hood in the darkenss with his cell phone turned on (or on stand by) how hard would it be to keep track of the spacker... They obviously can't teach their own to turn off the bloody celly properly so take another route...
Cheaper than smart dust networks reporting back to metal storm area interdiction arrays via all those little black helicopters....
Biting the hand that feeds IT
