The problem with games in general is that they are 1) made with restrictive and prohibitive DRM that's meant to deter pirates, but in fact only manages to make the game cumbersome and unattractive. You bought it and you can't even install it on two separate computers? ..and 2) made with a corporate mindset. How can we keep the player playing? How can we keep the reward-stream flowing? How can we turn this into a social network? So he pushes the game onto as many other people as possible?
Both of these decrease game value drastically. The result of #2 in particular is that lots of people will play it, but it turns into an unhappy necessity, an addiction, a chore. It does not flatter you as a company and it does not help the struggling PC industry. In my little world, lots of people pirate PC games because computer and console games in general have **** value nowadays. And companies do these things because they have to hold on to a struggling market and they think it'll counter piracy. Chicken or egg, I don't know. When in doubt, blame capitalism.
And ripster, you got a point there. I don't think that graph includes digital transactions though. That's the big money for PC games nowadays. Steam alone sells how much digital content, a billion's worth annually?