Airplay mirroring for iPad2 and iPhone 4s

Question

All my current, and less than 1 year old iOS devices, cannot use this feature.  How is it that I can Airplay movies and music fine but iOS 5 mirroring requires new hardware.  Come ON!

Answer 1

While this may be the most acceptable explanation, and probably accurate one, it would be nice to hear one from Apple.  While playing movies may be more computationally intensive than navigating through icons on your device, playing games with interaction may push the limits beyond usability.  This I understand and appreciate.
While I'm a big proponent of forward development, I do agree maintaining backward compatibility at the expense of performance doesn't exactly equate to innovation.  However, maintaining at least one release version, especially less than 1 year old,  isn't exactly asking too much.  Although we are all quite aware that purchasing new equipment is the convenient solution, you can't help having an audience with new technology and hardware purchased within the last year be somewhat disappointed.  This would have been a nice feature.  It is what it is.