Linux has always had a hurdle in the (probably mostly wrong) assumption that Linux users will pathologically not pay for software.
[1] http://www.reddit.com/r/linux/comments/17x0sh/john_carmack_a...
Plus a lot of these companies offer low quality ports and little to no customer support for Linux users, and if you don't use a supported distro then too bad for you. So again, what's the point? It's the same bad experience as using Wine.
Of course there are some who will only use 100% free/open source software for ideological reasons but these people are a small minority of Linux users in practise.
Most of the new indie game Linux ports work quite well in my experience though YMMV I guess. It would be unrealistic to expect support for every distro.
If there was a compelling collection of open source games I would certainly play them but that has never really been the case.
There are tangible advantages in having open source tools and components such as compilers,kernels and desktop environments even without every program on the system being open source.
Personally I do not derive pleasure from just playing games, I need to be able to study their source code and modify them. So I see no advantages in having proprietary games on my system. I hope that other GNU/Linux users acknowledge this as well. The one true value of the system is that it is GPL-ed.
If you look at places like /r/linux on reddit the Linux fanboys there are practically wetting themselves over steam.
I agree that more open source games would be a good thing, but I don't see it as necessarily more important than having access to the unedited recordings of a piece of music.
Seriously, because people sometimes pays for games, and that's OK, despite of whatever you choose to believe.
On the other hand, if one distribution emerges as the clear desktop leader (and no, Ubuntu isn't there yet) then maybe we will see support for it.
No one can really claim "year of Linux gaming" until we start seeing a wide variety of publishers releasing AAA titles. And until that happens, windows gamers will like it or not remain with Windows.