Not really, I've just browsed dells UK site and they offer several ranges of computers including a performance range all of which come with 5450 you can upgrade to have high performance graphics cards like 5870s, in fact the price is pretty damn good for the overall build I must say.
You can get expensive alienware style prebuilt machines which go over the top with performance components but that's it's own niche, getting reasonably priced gaming desktops from dell is no problem at all.
Again it's educating users as to what a graphics card is and why it makes a difference, if OEMS are guilty of anything its skimping on things like PSUs and motherboards limiting upgrade paths, that's done to make the PC more affordable at the end of the day.
alienware is extremely overrated