As has been mentioned myriad times previously, those people with Surfaces and transformer type Windows tablets generally have a keyboard/trackpad to hand.
iPad user and many Android tablet users do not have the input devices to hand.
Not to mention the larger tablet user base that IOS and Android have.
As a surface user I would use the keyboard in almost every single case except where I literally was unable to place the device anywhere, including my lap.
The desktop apps also support touch, in that the items can be set further apart etc. to help with the fat finger problem.
It will still be nice to have the touch version but it won't get used much.
Very useful for the folks having the tiny units at 8 inches though,