A pedantically correct, but ultimately pointless observation.
One can install and play a game bought from gog.com any time one wants, unlike with games bought from Steam, which have DRM, have to be activated online and must ping the Steam servers periodically.
Your example is valid, but there are plenty of other examples pushing in the opposite direction—for example PS4 and XB1 games delivered on physical media. Yes they'll play out of the box "forever" ... but in order to download important (occasionally critical) software patches you need the explicit blessing of Sony or Microsoft servers. And you could lose these for reasons that are wholly unrelated to your legitimate ownership of physical game media.
The PS, Xbox and Steam are all different incarnations of cloud services. They are very convenient, but ultimately don't offer any guarantees that one can play the games even a week from now.
At least consoles work without issue in offline mode, although MS wanted to disable that a few years ago, were confronted massive backlash and had to cancel their plans.
A big and relatively recent problem with consoles is that even offline games now more or less require a patch, because they're launched with major bugs.
One can install and play a game bought from gog.com any time one wants, unlike with games bought from Steam, which have DRM, have to be activated online and must ping the Steam servers periodically.