Siri could be limited to the iPhone 4S due to hardware differences

Wondering why Apple isn’t bringing Siri over onto older iPhones? At first we thought that perhaps it was a marketing gimmick, where Apple would attempt to leverage Siri as one of the key differences between the iPhone 4S and its predecessor. Now it seems that according to the guys at iFixit, a proximity sensor found in the 4S could be one of the reasons why Siri could be exclusive to the iPhone 4S.

The proximity sensor, unlike other proximity sensors which are activated when a cellular call is placed, is always on. This is due to the fact that Siri needs to be ready to take voice input at any given moment, so the proximity sensor is constantly sensing for when the user needs to input commands into Siri.

Of course unless Apple actually confirms this, we have no way of knowing although this is probably one of the better reasonings as to why Siri is only for the iPhone 4S, and to a certain extent it makes sense as well.