I can only imagine you must not have had to deal with a lot of those types of products in regards to maintenance before. Companies routinely change how they manufacture certain goods so it's close to impossible to find parts for the older models, for no other reason than you buy the newer model. Most of the time they will change the way they manufacture their products solely for this very reason. If that's not making a product and then dropping support a year later, I don't know what is.
In fact, with physical products the issue is even worse. You can actually buy products as new that aren't even supported by their manufacturer at the time of purchase!
Really, it's hard to compare a software company to manufacturers of physical goods, but I find that it's a fairly good comparison. In regards to software, Microsoft is hardly the only company that is guilty of that type of action. Medical management software, inventory control, actuarial software, and others all suffer from this kind of business model to an even greater degree than Microsoft's Windows.
I have a copy of Windows 98, and I can still install it. I have a copy of Windows 2000, and I can still install it. I have a copy of Windows XP, and I imagine that in 5 years I could install it again if I wanted to.