Earlier quoted context omitted.
Steam doesn't enforce DRM. You can usually go to the game files and just click the launcher from the file manager and the game will run without steam getting involved. Sure its not the most officially supported, but they hardly prevent you from doing it.
I think this is incorrect. I believe most Steam releases do require the Steam runtime to be present. Trying to open the game directly will "work", but that's because it's invoking the Steam runtime - just without showing the launcher. Examples: * Dead Cells has Steam DRM: https://www.pcgamingwiki.com/wiki/Dead_Cells * Hollow Knight does not (will run without Steam if you copy just the game files): https://www.pcgamin…
This is entirely up to developer to decide how they use Steam.
PS: I am game developer.