I think because most PC gamers build their own PC's from scatch and know what their want from they setups and most PC gamers just couldn't be apart from their machine.
Plus the PC platform is a all in one machine, it does everything.... as for games, as long as you have the basic knowage of PC's from what graphics card is best for you and what motherboard and ram gives that extra 3 FPS, your laughing.
Plus all the other things that PC gaming better (all depends on your setup).
Better graphics, tends to run games smoother (60fps using vsync), faster load times better resoutions etc As for HD, I don't think HD applies to PC gaming really as PC games have had higher resoutions for over a decade now and can go way beyond what a console can do (tbh, I don't really understand console HD vs PC HD).
Once upon a time I would of said racing, platform and fighting games were best left on the consoles but since you can connect your PC to the HDTV that doesn't applie anymore.
PC gaming rules.....