Actually, for computers, no this isn't true. The technology is changing, and not in minor ways, in significant ways. Most people continue to upgrade, but not all. But for a company to continue to support the old hardware / software costs a lot of money, more then they are making from it. Thus at some point they have to cut off the old equipment. If you have a processor that just can't perform the operations either you have to code more complex code to detect these processors and run equivalent code to make it run, or have separate builds. Separate builds cost a fortune, and equivalent code even if not executed still has to run through the processor detect and thus slows down even more and not just on the old processor but slows down the new processors as well (just not as much).
In the case of Apple, they changed processors completely! It would be more like the auto industry switching, in one season, from gasoline to all electric (not hybrids) and then 20 years later saying that they won't make spare parts for the old gas engines anymore.
At some point you HAVE to cut off the old, it just isn't feasible to keep supporting out dated equipment.