Steam could be used simply as a distribution method, you have an account to purchase and download. The level of DRM protection is up to the developer/publisher

Steam could be used simply as a distribution method, you have an account to purchase and download. The level of DRM protection is up to the developer/publisher to decide. It's possible for the game to no longer require Steam once it has been downloaded. Although, if the developer/publisher doesn't include an installer of some sort within the game files reinstalling without Steam might be a bit tough. Makes me wish for the old days when you didn't need installers, you just zipped up the folder as a backup. Need to reinstall? Unzip to new folder.