Why are there no full-sized keyboards with multitouch trackpads?

So I've been looking for a new keyboard for a while to replace my elderly PS/2 Logitech. While I use a mouse almost exclusively (even with my laptops), I would ideally like a full-sized keyboard with a multitouch trackpad for useful Windows 8 gestures (and general improvements in scrolling, zooming, etc...).

The trouble is, no one makes one. Logitech makes the K400 which is almost what I need, except that it's about 25% too small. It feels more cramped than the keyboard on my 12.1" tablet PC, which is pretty unacceptable for use with my desktop.

This kind of keyboard is tailor-made for Windows 8. So why hasn't Microsoft (or any other OEM) made one yet? I have no interest in cluttering up my desk with an extra standalone full-sized touchpad accessory which is expensive and extraneous, I just want to a little 2" square to do some edge swipes and two-finger gestures from...