When I started gaming again, I just bought a 360. Rather than dual-boot, I just hit the 'swap input' button on my monitor and get to fraggin'.
I really don't think that arrogance is the reason linux is not being adopted by more people. There are friendly resources available all over the 'net ... this forum, the official Gentoo and Ubuntu forums ... they've all treated me well.
The reason is more complex than that. Most people don't like to take chances with something they barely understand. My mom hesitates before every mouse click in Windows .. there is no way I could convince her to try linux.
I'd also point out that the majority of those who do tinker with their PCs and are comfortable installing OSes and what-not are also gamers. We all know, despite brilliantly written HOW-TOs in MPC, that gaming and linux do not mix terribly well.
Until linux is a 'drop-DVD-in-slot' installation that includes all the software the average user will need, it won't gain a significant amount of market share.
This sort of leads into a totally different debate of PC games VS Console games. I have two cousins and a step-brother who love their consoles. I've spent a bit of time with ever major console since the NES (when I say major, I mean the usual offerings from Sega, Sony, Nintendo, and Microsoft), and I've never gotten the same gaming experience as I have using a PC. Maybe it's because I'm older and can understand the rich story lines, maybe because I spent more on my gaming rig than two PS3s and something deep down inside makes me feel more because I invested more, maybe it's the graphics... Who knows? All I know is I think PC games are better. Leave the console for Sports Game 0-whatever and Animal Crossing. Leave the real gaming to PCs.
While I think Linux would be very welcome to the consumer, it's not worth the inital learning effort for most people. Once I learned a bit about Linux, the way the filesystem's laid out and what each directory is for, some basic commands, getting familiar with the apps, Linux is stupid easy. Couple those basic items with a simple understanding of computers and Linux is a perfect fit. Unfortunately, people don't want to take the time to learn such things.
Hell, even with Windows, most people don't really know anything about windows aside from the web-browser, the "Start" button, and Windows Media Player. Everything else is completely foreign to them. All of that crap and more is available with Linux after installation. All they need is something close to looking like a start button (Kubuntu anyone?) and they're golden.