While I personally have nothing against Linux, I cannot fathom what kind of person plays games on it. The OS simply isnt for gaming. To expect DB to not only create for Windows, but two other OSes, is a bit silly in my opinion, ESPECIALLY when it is such a small crowd. I personally don't know a single person in real life who uses, or has ever used Linux.
I understand what you're saying here, afterall, I have a similar sentiment to the Mac people, whom I cant understand complain about not having some latest game come out on their most endeared Apple system yet continue to think their system is even greater than sliced bread.
But then I have to come back to reality when I realize that I have the same issue when it comes to not having games made for Linux.
At the risk offending you though, I have to disagree with your understanding of the situation. Its a bit of a chicken and egg story and its based around demographics. If you don't know anyone who uses Linux, then you are (probably) in the Windows demographic, and that will always determine your perspective. Professional developers perceive that only WIndows people buy games, so they only make games for Windows. Linux people have largely given up expecting games to be made for Linux, so they run a Windows system just for games and stop complaining.
Another thing to consider is that Linux generally attracts the technical folk, because lets face it, who sells Linux preinstalled systems that the public will happily run out and buy? No, its not happening. Instead, the more technical folk will take older machines or build tailour made systems and throw Linux on it for their own use. Incidentally (and somewhat generally speaking), its the technical folk who have a history of hardcore gaming, and thus its them (me included, I guess) who would love to see our favourite passtime come to our favourite OS. Oh yes, and there are a lot of us, percentage wise we probably rank pretty low, but in physical numbers, there are several million of us around the world, and growing daily.
Some closing thoughts: Linux is free, is improving and evolving far quicker than other OSes, and provides a fantastic workbench to a lot of developers out there. A lot of independent game developers are growing up using Linux and hitting the market with deep Linux skills. And there are some interesting changes coming to the Linux ecosystem which will provide, er, game changing elements for writing games in. I think (hope?) it wont be long before Linux will become a serious contender for a gaming platform. The trend is certainly starting to look that way, if the interests in Steam and the Humble Bundles are any indication. And the limitation is not the OS, but the will of the people.