I am by no means a fan of Microsoft's, but when you release an OS and some applications and provide security fixes for ten years, asking for people who want to continue using that OS/app beyond that point to buy a support contract is not a complete dick move. In the FLOSS world, you may get volunteers who maintain a piece of software as a labor of love, but with something like Windows or IE, someone needs to pay people to do that work.
It might make sense to create something like a foundation to take care of the long term support for software, which would benefit everyone. I'm kind of surprised actually that this has not happened, yet (to my knowledge, at least).
But more than likely it is because deploying to that 1 customer is always going to be easier that deploying it publically.
The way I look at it, MS obviously is actually continuing to support the product, they are just choosing not to make it available to most people. It's still supported, just not for everyone.
I feel that if security patches are still being produced, they should be released as opposed to expecting people to use nothing, or roll their own by getting patches from a third party.
They could be released as "donations" to the public good from the big customers.