Re: PC games?
Steam wouldn't exist without Steamworks, and even the KSP devs say that they are selling through Steam because for whatever reason, there's people who will ONLY buy games through Steam (despite the game being available more cheaply direct from their own website). They've stated the game will remain available through their website for the forseeable future, and as far as I'm aware, in a pitifully rare exception for games in general, they're not using Steamworks or any other DRM. Therefore, KSP will actually work without Steam running. Hell, you can just copy the game from your Steamapps folder, put it where you like and it will still run.
However, Steam would not exist without Steamworks, and you can "offline mode" me as much as you like. "Offline" mode isn't, and you know it. Unless of course I can install and run a Steamworks-hobbled game with no Internet connection whatsoever and without logging into Steam, and with a guarantee that nothing is going to phone home to anybody in order to decide if I get to continue having the use of a toy.