You make an interesting point. I think it falls down when you
consider that if Ford had a demand for Model T support, they
certainly would be meeting it. There is still a demand for XP.
M$ is ignoring the demand.
Well, having worked for Hewlett Packard, I know that they had a projected
product support life. Of course, hardware has a problem. I worked on one
product for which the original source of one particular part stopped
manufacturing the component. Guessing HP was their sole customer, and the
cost of production exceeded the revenue generated by sales.
So, hardware changes over time. My HP Pavilion 6745C runs Windows XP Home
Edition poorly; slow as molasses in January. But it only has 256 MB of RAM,
and anything under 512 MB of RAM is woefully inadequate. Cost of upgrading
to 512 MB is excessive; and the computer is incapable of supporting more.
OTOH, my HP Pavilion m7590n shipped as, "Windows Vista ready". Given how
little difference there is between Windows Vista and Windows 7, upgrading to
Windows 7 went well. But I expect this hardware will be deficient for
Windows 8. I already had to replace one hardware component because of
obsolescence, and wonder if continuous hardware upgrades will be worth it in
the end.
The later versions of Windows are designed to take advantage of newer
hardware capabilities. Computers are relatively cheap, compared with prices
twenty years ago.
The reason the Model T is no longer built, or even supported, is hardware
upgrades. I don't see how that is different for computers.