You do realize that Microsoft has to stick to the years of support they said they would maintain from when Windows 7 and the others first came out, right? Businesses and consumers bought with those years in mind.
Pushing people to 10 does not help them in any way. Keeping 10 and continuing to upgrade that will be what keeps the support on Windows down, over the years, though.
That is part of why MS gave 10 away free with a 30 day rollback limit...to try to encourage those people to jump ship to the new OS, theoretically reducing the pool of people who will need support on the older systems as they creep toward obsolescence.