Orion and BobnSpike,
If I may, another reason is to preserve the undercarriage and the airframe. On a long runway the aircraft will probably eventually get airborne but at a much higher speed. Unless the runway is glass-smooth every little surface irregularity will be very forcefully transmitted to the hull.
On the 767 mentioned earlier there must be a weight/lift/temp etc curve that allows the flapless takeoff procedure, i.e. with certain weights and on certain runways it's allowed.
My only experience of such a takeoff was years ago on a Vasp 737-200, GIG/CGH, between 30% and 50% full. It took ages, rattled and shook like a Model-T Ford on a rocky road, overhead bins opened and handluggage fell out.
I am not a pilot nor am I any longer associated with aviation. But I'd venture a guess that a takeoff like the one just mentioned would take a toll on the hydraulics - and much more - equivalent to several years of normal operation.