Why exactly? I dont see many pilots flying around going "lets shove them leavers forward a bit more, that will teach them! Mwahahaha!" Im sure none of us lower our standards/operate outside of SOP just to 'show them'.
Even operating within SOPs you can be more efficient, things like requesting non-duty runways, track shortening, efficient altitude planning with regard to wind, temp and weight. You might end up saving at most 5% fuel but it is a huge figure in the annual report.
Disengaged pilots will tend to sit and just fly the routine sector rather than be proactive and save the little bits which add up in the end. At the extreme some pilots may go out of their way to fly a slightly larger circuit or conduct approaches when not required etc... this will easily add large numbers to the cost factor while being perfectly safe.