So most of the entire world is using windows/mac if they want to do something serious other than web browsing. And most of the linux desktop usage is contributed by enterprise and office pcs using linux. People still use windows and mac on their personal pc. So it is not a huge win if you want developer support for games and apps. Even if developers follow these numbers and start supporting linux, they will soon realise it is not worth their time because linux usage is mostly due to enterprise running chrome.