What is insane? Windows 7 is 8 years old. Windows 8 is 5 years old. Microsoft is still providing security fixes for what are essentially now legacy platforms.

There has to be a cost in supporting these new processors. Windows runs on almost anything and the cost of testing updates across various platforms has got to be huge.

I also think it is a great way to reduce fragmentation. Windows 7 is supported till 2020. However you do not want to just cut people off. If you can reduce / stop new instalations before then it will greatly reduce the number of unsupported machines when Microsoft cut the cord.