I have a strong feeling that most gamers these days are buying more games than they are actually playing. My personal theory is that there is a LOT of content on multiple platforms and simply not enough time these days for the average gamer with school, family, job, etc. to keep up with it all.
Every few years or so i'll read an article that talks about gamer's buying habits versus how much of that content they are actually utilizing. The results are usually pretty surprising, indicating that quite a large percentage of gamers are purchasing, but not actually playing or finishing their games all the way through.
Case in point: Stardock did a recent study on their title Demigod. They found that a little less than a quarter of the people who purchased Demigod bothered to try Demigod's multiplayer features. In this particular study Stardock defined "try" as clicking on the multiplayer option in the main menu and fiddling with it's options. So in this case, the vast majority of gamers who purchased the game didn't even bother to click on the multiplayer option, even though Demigod was a multiplayer oriented game.
In another relatively recent interview, Peter Molyneux was talking about a Lionhead study of Fable II user habits they conducted during their preparations for Fable III. They found out that roughly 50% of gamers who bought Fable II used only 50% of the features offered in the game.
