Yeah, but windows XP doesn't belong on core i7 4gb+ ram gaming systems. Though, sadly, people still gimpify said machines with XP because of their unwillingness to change. However, there's a lot of people who aren't going to give up 7 simply because 8 takes away too many known and loved features, and it doesn't bring any real hardware/software support to the table that grants incentive to upgrade.
Windows 7 had plenty of reasons to get it over XP, with it's rebuilt audio and graphics system, native 64-bit support for 4GB+ ram, dx10/11, native SSD trim support, usb 3.0 support, native SATA-from-install support, better and more efficient native support for multicore CPUs. List goes on and on. Also, the UI looked prettier (at least for me) and composited desktops have their advantages. Start Menu search being added was another huge one, nothing is as nice as being able to hit winkey+a bit of text+enter key and run whatever program you have installed. Windows 7 brought a lot to the table, while keeping things familiar and beautiful. Also runs like a charm. Also more secure than XP out of the box.
Windows 8 revamped everything people were familiar with, and a lot of people don't like change. They also took away Aero, which I don't like (though they kept the DWM technologies that composit the desktop). The security increase is nice, but it's not foolproof or even breathtaking. No new technologies are being exclusively supported by 8, except for maybe tablet gadgets. You're not going to be able to use more RAM, more processor cores, have better graphics drivers, or anything like that going from 7 to 8. It's just different, and maybe moderately improved (and even then, for the sake of handheld devices).
If people don't wanna jump to 7 from XP despite all its advantages, even to the point of not fully using their hardware because they want to use XP? They're not going to get 8, for sure. Not till XP stops working, period.