You can archive the installed files from Steam though. An example is the pixel art program Aseprite. The devs said just to copy the binary out of the Steam folder and place it elsewhere if you wish.
But it won't launch without being logging into your steam account
That's still not "archiving" though. It's one thing to download the installer, and quite another to install the game and copy the files hoping it will all still work. Especially on windows when registry entries are involved.