And if they did put out a PC, if the game ran poorly, would you buy it? Probably not.
See what happened to Deus Ex: IW for putting a PC port demo out -- it destroyed the game's chance of PC sales upon its release. People expected the game to turn out that bad technically on the PC, given how the demo turned out.
If ports aren't ported that well to the PC, we probably shouldn't expect a demo for it.