Have you ever tried to install Windows on a new PC?
Have you ever dealt with non-techie Windows users whose system is broken?
The only reason you can say that is because OEMs ship systems with Windows pre-installed. If they shipped systems with Linux pre-installed, they'd be no different. And it only takes a few clicks for a non-techie Windows user to trash their system installing random crap from the Internet... yes, you must have Happy Fluffy Kitty Screen Saver right now!
As for Linux gaming, the problem is that most of us who have Linux systems also have Windows systems for games, so we're unlikely to switch. I installed Linux Steam on my netbook, but it can't run many of the Linux games I own because it's so low-powered.