"Current Plan" to Not Bring Siri to Older Devices, Proximity Sensor to Blame?
Apple will not support Siri on older devices. No reasons have been given as to why despite developers successfully porting the digital assistant to the iPhone 4 and 3GS.
Michael Steeber received an email from Apple’s tech support claiming “Siri only works on the iPhone 4S and we currently have not plans to support older devices.” The “current” plan is to not support any other devices. However, plans change, and the evidence is mounting against Apple that there is no reason to not support Siri on other devices.
A number of other posts, including iFixit’s breakdown, have commented on the slightly modified proximity sensor. iFixit noticed that the new sensor has an infrared LED light that controls when Siri is activated. Whenever the LCD screen is activated on the 4S the infrared LED is shining as well, which means its ready to let Siri know when the phone gets close to the user's ear. On the iPhone 4 the proximity sensor is only activated when a call is made or received.
This explanation seems bogus though. A simple software update could go a long way to changing the way the iPhone 4’s proximity sensor works. Additionally this small limitation does not inhibit the way Siri operates in terms of accepting and executing voice commands.
Siri is still in Beta and Apple is constantly updating the digital assistant. The company at any time could change their stance and bring Siri to their older devices. There are no technological limitations preventing Apple from doing so. My guess is Apple wants to make sure their servers can handle the demand, support as many languages as possible and add another level of polish before releasing Siri to other devices.
Oh and they want people to have an additional incentive to buy the iPhone 4S.
Source: Michael Steeber