Not to mention Apple especially does this. 68K -> PPC -> Intel, OS9 -> OSX, ditching Rosetta, and ultimately forcing everyone to update OSX regularly. My fiancee's Mom was forced to update to Mountain Lion to play her latest games, when Snow Leopard was more than fine for her.
The Macintosh has been around for 30 years. Three major transitions during that time doesn't seem like an abnormally high rate of change to me. DOS-based Windows -> Win95 -> NT during the same period is pretty close.
I also find it hard to blame Apple for the death of 68k and PPC. If you know what the dominant processor architectures will be in 2035, please tell me which stocks to buy :)
The DOS -> W96 -> NT transition didn't break compatibility. You can still run your DOS programs on your Win8 machine[1].
Powerbooks and iBooks, on the other hand, are paperweights today. Machines made in 2005 should be usable today (and indeed, the '05 Windows machines are still usable today).
[1] with Dosbox or virtualization, but that's not the point. Any similar measure is not available to run your m68k, ppc/classic or ppc/osx applications.
