People who are really into high end games will often want to build their own machines (or get a friend to do it , or buy an alienware PC).
This means that gamers are very price/performance sensitive when it comes to buying the computers, I know this is a reason that many of my gaming friends will shy away from choosing a Mac when it comes to buying a computer. They would rather buy the PC for the same price as an iMac because with the PC they will usually be able to get a higher end graphics card + upgradeablity for the same price.
if Linux became a viable gaming platform then they will be able to buy the same sort of PCs they always did and will be able to re-invest the $100 or so they would have paid for a Windows License in faster hardware.
1. Linux users are much nerdier.
2. Nerds play more video games.
* Windows appeals to people who want to be in majority. This makes them feel comfortable. Of course, it has a stronghold in business world too.
* Mac devices are seen as status symbol. It's elegant, 'just works', 'stylish' 'gorgeous'. And they don't use it /despite/ highish cost - they use it in part /because/ it's expensive. You don't actually need to do anything with it, it's enough others see you have it.
* Linux appeals to people who like to brag how much they can do. Tweakers, tinkerers.
Why bypassing OSX? And why would linux support cause a flood of Linux games when it hasn't worked for OSX?