Once more; in case of Steam it's up to the developer/publisher if any kind of DRM is shipped.
Steam/Valve does not enforce DRM in any form. Yet, it does support it.
There are games which don't come with DRM.
Once installed, you can launch them right from the corresponding SteamApps directory without a running instance of Steam.
You can even copy the game folder to another computer (yes, without Steam) and launch the game without issues.
If the game supports Steamworks (achievements, Steam community stuff, etc...),
you have at least account-based DRM as Steam has to run.
But even in this case, some developer/publisher provide an alternative binary _without_ the Steamwork features (see link above).
Again, it's up to the developer/publisher!
Compare that to Ubisoft's Uplay and EA's Origin.