Fallout New Vegas required users to register their game through Steam. You could not opt out of Steam, even if you didn't purchase the game online. You either registered through Steam or you didn't play. The only other option was to play on consoles.
Steam is an awful form of digital distribution, despite its very loyal and obnoxious fans. Steam must be active in order for your game to run. You must be online to play. You can go to offline mode for a short time, but you must return online to continue playing. Other online distributors do not require any of the above. You just get your key, download, and play to your heart's content no matter where you are on the planet.
Steam does not require constant connection to the internet, and you can use it on the offline mode. Only a one time online activation the first moment you launch the game. I don't see why it's so bad to register to Steam, it's a great service, free and full of nice features such as:
-Automatic patching
-In-game guide
-In-game internet browser
-In-game chat
-Great online community
-Easy DLC distribution
-Achievements
-Stats tracking
99% percent of gamers have internet access, so it's very easy to just install Steam, which is just 2mb, activate your game and play for the rest of your life without any need for constant connection like Ubisoft's DRM.
I'd rather have Steam than Games For Windows Live, that thing is full of glitches.