Piltdown Man the tone of your posts imply that a flight planned routing through controlled airspace is merely a planning technicality and once airborne direct routings outside controlled airspace should be offered by ATC as if by default?
I don't understand why you would assume ATC will automatically send you off-airway? Have you any company SOP regarding the dismissal of radar control in favour of a reduced service to make shortcuts? The policies of more and more passenger carrying operators not least the experience of pilots familiar with the burden of safety responsibility these days promote sticking to the assigned route. To explain a TCAS Resolution Advisory in Class G airspace to your manager when you left the airway merely to make a shortcut would not fall on sympathetic ears. Much as I know a shortcut through no-man's-land would save two or three minutes or 100kg of fuel I won't do it unless for reasons of safety.
Personally, and I don't have many understanding First Officers over this, I don't ask for direct routings from ATC but rather wait until I am offered. There is something about asking for "directs" that I have never been comfortable with; it feels to me as if I am trying to tell the controller his job. Unprofessional in my opinion. Feel free to argue to the contrary though; I may change my opinion if someone can offer printed guidance which has until now escaped me.