Because them showing off the PC version would leave the console users disappointed and claim false advertising.
It's better to show off the worst console graphics-wise.
The PC version will be miles better graphically, simply because of out of game tweaks a.la .ini, higher resolution textures have been confirmed by gamesas, on top of graphics sliders allowing for more details than consoles allows, and that's not even counting mods and texture packs.
No. It will be better, but not "miles" better. If you set yourself up for "miles" better, you will be disappointed when you finally see that the PC version isnt that much greater, just better res. Be happy with that. Take it or leave it.
And no, bethesda didnt show off the console version for that reason. "false advertisment". Really? You really think thats why? Sorry, but that is a really dumb assumption, and it only goes to show that your being a PC elitest right now. Stop it. Immediately. If that were true, then why is all the footage on BF3 out right now is basically PC? Todd prefers Xbox, he has said it VARIOUS times. Im a PS3 gamer by the way.