A friend of mine pointed out this little tidbit.
Quote:
Initial installation requires one-time internet connection; Ability to save game, earn achievements, receive title updates and online play requires log-in to Games for Windows LIVE; software installations required including Microsoft Visual C++2008 Runtime Libraries, Games for Windows LIVE client, Games for Windows LIVE Client Patch, Sony DADC SecuROM, Microsoft DirectX.
I'm still trying to comprehend why this was all deemed necessary for the steam version. I'm guessing money.