The support of older devices makes me feel ok about plunking $1000 on a phone, and $400 on an iPod.
Also, I've turned several former Android users into iPeople by giving away my old, but still supported iDevices.
So there is significant financial benefit to Apple in continuing support as long as feasible.
There is a TON of anger being directed at Google right now by Android users who are sick and tired of spending so much money on immediately obsolete devices. They are quite envious of the treatment we get from Apple.