An OS has to start somewhere, Windows has always been the majority holder in PC gaming, and has been for many years. You might ask, then what's the point. There are multiple reasons imo why. You save, that always shitty fee when building a new PC of having to factor in Windows, also helps the sale of gaming specific PCs, they might drop in price a little and get more people into PC gaming.
All you need is that 1 big company to full take on Linux, and others will follow. We are already seeing this due to valves efforts.
http://www.polygon.com/2013/10/12/48...field-director
About this time is a great time for this too. The whole Battlefield 4 runs better on Win 8 then Win 7 (proven btw) has pissed a lot of people off, because people now they feel they must buy Win 8 to get the best performance, and at the start it fixed a lot of stuttering issues and crashes, while it's only 1 example, it only takes a few for people to get pissed off enough to try something like Linux. (if it's available).