They're giving away Windows 10 for free. So they're copying Apple's strategy and instead of back-porting, just get everyone onto the latest version.
I honestly thought IE11 would be the last major IE release, guess I was wrong. This new one looks no better.
In any case, I'm not doubting that it's easier to pitch an update if it's free. All I'm saying is that purchase cost isn't the main or only barrier to Microsoft software updates.
Serious I think I am not alone in wanting to be able to run snow leopard on recent hardware. Apple please make software as good as your hardware.
New Windows licenses, licensing on lots of other software, MSDN, enterprise support, and all the things that aren't upgrades of existing Windows licenses.