Not always. There are plenty games that work without the Steam libraries. Also GOG exists and very healthy with explicit no DRM policy.
GOG isn't exactly DRM-free these days. The platform doesn't add its own DRM, but it does distribute games with DRM elements. Their stance seems to be that, so long as the game is playable offline in single-player mode, it is acceptable.
But GOG censor their catalog for everyone after feedback from the CCP cough gamers.
GOG isn't exactly DRM-free these days. The platform doesn't add its own DRM, but it does distribute games with DRM elements. Their stance seems to be that, so long as the game is playable offline in single-player mode, it is acceptable.