PC games are written to the lowest common denominator. Since most people dont get DVD-roms with their computers, they dont make games on DVD. Of course a lot of people would buy one when it eventually became necessary, but consumers are as unlikely to make that jump as publishers are. There is something about the PC gaming arena that totally stifles innovation, but unfortunately, game publishers refuse to band together to do something about it. PC gaming is getting stale, quick.
I was in software etc the other day and some old man was looking for a game that would torture his video card. He looked around at quake 1, said hmm, requires pentium 90, I think I only have a pentium 24... I stopped short of handing him UT2003 even though it was sitting in plain view. The very people that game companies are trying to appease are the very people who wouldnt know a megabyte from their asshole. All they need is to collaborate and come up with a big fat logo to stuff onto PC games that require power. Following DirectX generations should be fine, but it should be more all encompassing, including CPU and other hardware requirements.
But will that ever happen? Nah.