Very few non-classic and/or popular cars receive massive aftermarket support for all parts - often the aftermarket supports parts that are in common with a lot of vehicles or are vehicle-agnostic (such as belts, etc), and in some cases you're plain SOL (try replacing an airbag on a 1993 Dodge Caravan, for example - all you can find are OEM used ones pulled from junkers).

I think your comparison would be more apt if, say, Ford disabled all vehicles that were 10 years + 1 day old. While Apple isn't disabling your OS, they leave you exposed without security patches, etc... - making it approximately the same.