neumi5694: You can also create backup installers for your steam games btw. Sure, you still need the client to reinstall them, but it's not online.
As a last resort, you can always just backup the installation directory and be done with it. The GOG installers don't really do much more than unpacking files and write a entry into the registry that the game was installed.
For DRM free games that will work just fine, if Steam ever gets shut down for good.
I bought DRM free games which cam without installer from Gamejolt, itch.io and other platforms, they were just zip files.
Does that mean this distribution method is inferior to GOGs way to do things? Maybe, but it works.
I would actually prefer if GOG offline installers were just zip files that you decompress to a folder of your choice, and run an executable to start playing. Hopefully it wouldn't make any changes to the system (Windows registry etc.) on its own, though.
Then the installers would probably be smaller too, than what they are today. It would also be much simpler to archive them, test their integrity etc.
However, that is not what the Steam DRM-free games are. You can't easily just download 1000 Steam games as zip files from Steam servers; instead, you'd have to install them one by one, compress the folders to zip files, and uninstall each game. Much less convenient that the GOG way, especially with 3rd party tools like gogrepo.
I have 2370 games on GOG, and I'd hate to think about the amount of work trying to install + compress each of them one by one from Steam, AND doing that same whenever some of those games receive updates.
With GOG, no sweat, I have almost all those games' offline installers on my hard drive, except for a couple that I just bought this week, and if there have been any updates since last week.