Even if all games were FOSS, without - at least - a stable API, most games will remain a hassle to run. DOOM doesn't deal as much with this due to the high amount of volunteers, but relying on community support for all games is just outsourcing labor to some unlucky fellows. At best, it's yet another pain for Linux users. At worse, it's the death of unpopular games. Either case, a hurdle for Linux adoption.