...it is possible that direct routing is not fuel or time efficient... Great circle routes and/or 'preferred routings' (that take in wind effect)
Very true.
A straight line on the controllers screen is not necessarily the shortest distance between two points... in time or space (Do you know, or can name the geographical projection that your screen or map is based on? When was the last time you checked the wind?).
As for preferred routings... the Flex Track supervisors in Melbourne would become very unhappy if controllers gave short cuts to aircraft flying the daily published optimum route for wind and fuel consumption. Something a number of controllers had some difficulty in understanding.
To throw another scenario into the discussion... what's the point in track shortening an aircraft that has reduced speed due to "no parking bay available for us"?
Or, as happens in this part of the world... track shorten every aircraft to the three sequencing gates and reduce the space between them down to the absolute minimum as per the Letter of Agreement, only to sit back and feel good about yourself whilst you watch the receiving controller give them 90 degree turns or holding patterns because he has to blend the three trails into one with a tenth of the space to do it within?
Sometimes direct tracking doesn't help.