"If there are hundreds of thousands of Linux users playing Quake Live when we are done with Rage, that would certainly influence our decision"
Enough is said with that statement right there. There simply isn't a big enough market for it, and if it pisses off the 2% of the gaming community, so what no loss to them.
One should know better that if you plan on using Linux as your main OS you are going to have things that are just not supported, that includes games.