While many publishers today see the PC as a handy way to make a quick buck on the side - see Capcom for reference - not everyone thinks releasing major titles on console and PC simultaneously is a good idea. Like, Microsoft Europe don't. Indeed, Microsoft Europe's Peter Zetterberg thinks it's a terrible idea. Why? Because while many people have PCs, not so many people own 360s. Using the German market as an example, he says:
If we launch a game that is on 360 and PC simultaneously, we basically shoot ourselves in the foot by allowing the German market to choose to play the PC version - because they are more likely to buy that than spend their money on the Xbox 360.
MGS Europe: Simultaneous releases would "shoot ourselves in the foot" [GI.biz]