First interesting thread on here for a while, although I suggest that the title be changed to reflect the thread drift.
Anyway, my tuppence worth:
In European ops I make a point of asking for short cuts on every flight, and think its fair to state that 80% of my requests are obliged. I would estimate that only 20% of the time ATC beat me to it and offer a direct route.
Generally short cut requests are greeted with "stand by" and I assume that this means a call to coordinate the request. I don't fully understand what goes on behind the scenes in ATC, and I am sure ATC don't fully understand my operational constraints, but I am convinced that short cuts are mostly made available to those who ask. Those who don't ask (and I am not talking USA here, which we all know is completely different), don't get.
I estimated the 20% and 80% figures by the way - but just wonder if by any chance it bears any resemblance to the old adage - 80% of the work is conducted by 20% of the people.