Same reason why Apple doesn't put a lot of time to MacPro anymore.
Same reason why Apple sells iPhone without replaceable battery while most phone does.
Same reason why Apple sells computers with mediocre graphics.
I use Apple, love SOME of their products (the number is getting smaller and smaller each year). But being an Apple fanboy has been long way off to me.
Apple doesn't make all things that fits me. I wanted a MacPro with GTX690 and SNB-E CPUs instead of gaming machine. But instead Apple only came up with iMac using a mobile GPU.
So I stopped asking questions, took the slap in the face and just use whatever tools available at hand. Just get 1080p HDTV like most people do for games console.
iMac use 1440 display.
So anything lower than that looks crap anyway. PS3 or Xbox doesn't come with AA/AF adjustment and everything is upscaled from 640p or something except for the UI. I doubt you can enjoy it. So, why bother?