I don't understand why they would do this. If I was a microsoft manager I would be glad something like this happened because it would force people off of old OSs without having the bad rep of doing it through nag popups. Now everyone on XP will feel safe because its still getting updates.
In the real world, there understaffed IT departments, insufficient budgets, time-consuming logistics, and complex systems which are not easily upgraded. Microsoft's options here are either "to hell with it, not my problem, just let the world burn" or taking responsibility and fixing problems which will affect people.
I do appreciate the problem of security patches, but XP is pretty rock solid as a platform so for many businesses their tool does what they need.