First, with MS-DOS, then with Windows, then Windows NT, Microsoft managed to get customers to upgrade, time and time again. This in itself isn't a bad thing.
Most companies make products which they improve on again and again.
It's not uncommon for software companies to support two or three versions of a product at any given time. The intellectual property is no longer valuable to them. The present day goal of selling the newest version of the product, the most financially capable product, takes precedence. To any tech CEO, this would seem like common sense. But that's where the second part of the Microsoft wheel kicks in.