If you've ever tried to run a hardware business (or really any business), you know that it is not financially sound to continue to support old devices that have been superceded (sometimes more than once) by newer products that consumers are currently spending money on.

We can debate if this is the way things should be, the aspect of whether you truly "own" things, software escrow, and on and on. But the phenomenon itself is in no way unique to Apple. If anything, I have found that the usable lifespan of Apple hardware is, on average, longer than the usable lifespan of other name-brand electronics in similar categories.