@Tabeer - Actually, because there were so many Chinese users who don't pay for the license and use pirated versions, they made the upgrade for free for such users around the world as well.
I think that the promotion is over though, so it's logical if it doesn't display anymore for users.
Another thing is that there are still recurring updates in all Windows versions to get Windows 10, compatibility and telemetry updates, "Get WindowsX" icon, a new Windows Updater and etc, all related to Windows 10 and its features. They prompt you to upgrade and get the new version of their OS like it's necessarily better for each person, corporation or they habits and use of computers.