Forcing upgrade to Windows 10 is preparation for micropayments.
Microsoft's next step after they get everyone onto Windows 10 is to start charging a little it for everything.
Want to use a third party browser? $5.
Want to save files that are open? 10 cents per file.
Want to change your theme color? 99 cents.
Want Windows updates? Those will be $2 each, and if you don't install them your operating system will cease to function.
Pretty soon after that Microsoft will start force installing updates and debiting your bank account without permission, and you'll allow it because Microsoft spends more on lawyers in a year than your government spends on health care.