The dualboot issue is important here. Since most people who go out of their way to install linux on a computer are probably savvy enough to setup a dualboot it

The dualboot issue is important here. Since most people who go out of their way to install linux on a computer are probably savvy enough to setup a dualboot it removes a lot of the economic incentive to port games to Linux. This is because they know that most serious Linux using gamers will probably dual boot anyway so a Linux port of a game is a "nice to have" but won't stop somebody buying a game.